Re: [Xen-devel] [PATCH v3 09/35] OvmfPkg/OvmfXen: use a TimerLib instance that depends only on the CPU
On Mon, Jul 22, 2019 at 09:28:20PM +0200, Laszlo Ersek wrote: > On 07/22/19 15:49, Anthony PERARD wrote: > > On Mon, Jul 15, 2019 at 04:22:19PM +0200, Roger Pau Monné wrote: > >> On Thu, Jul 04, 2019 at 03:42:07PM +0100, Anthony PERARD wrote: > >>> ACPI Timer does not work in a PVH guest, but local APIC works on both > >> > >> This is not accurate. It's not that the ACPI timer doesn't work, it's > >> just that it's not present. The PM_TMR_BLK should be set to 0 to > >> indicate the lack of PM timer support, or else there's something > >> broken. > > > > I'll reword that first sentence. > > > > OVMF doesn't look at the PM_TMR_BLK value when initializing that timer, > > it only looks at the PCI host bridge device ID because OVMF is built > > with QEMU in mind and there are only two possibles choices, QEMU is > > running with a piix or q35 machine type, I think. > > We should split this statement in two. :) > > OVMF doesn't look at ACPI payload because it is a design goal to keep > the guest firmware un-enlightened about such ACPI contents that arrive > from the hypervisor. Parsing ACPI in firmware always looks attractive > until someone actually writes the code, and then it always ends in > misery -- at the latest when people realize they have to parse AML. > Parsing ACPI is only feasible when you have a full-blown ACPICA (or > similar) subsystem, and edk2 doesn't. Therefore, OVMF looks at either > hardware, or specialized paravirt information channels such as fw_cfg > files, that are easy to parse by design. IMO passing information using such side-channels always looks attractive at first sight, until you realize at some point later that you just have ended up with a completely custom interface that duplicates ACPI. Having that said, Xen manages to get most of what it needs from static ACPI tables, but I'm not sure if OVMF could manage to do so also. Xen has quite a lot of baggage here, like using xenstore/xenbus instead of PCI, or custom 'start info pages' instead of ACPI, which we are currently trying to partially move away from when possible. Thanks, Roger. ___ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
Re: [Xen-devel] [PATCH v3 09/35] OvmfPkg/OvmfXen: use a TimerLib instance that depends only on the CPU
On 07/22/19 15:49, Anthony PERARD wrote: > On Mon, Jul 15, 2019 at 04:22:19PM +0200, Roger Pau Monné wrote: >> On Thu, Jul 04, 2019 at 03:42:07PM +0100, Anthony PERARD wrote: >>> ACPI Timer does not work in a PVH guest, but local APIC works on both >> >> This is not accurate. It's not that the ACPI timer doesn't work, it's >> just that it's not present. The PM_TMR_BLK should be set to 0 to >> indicate the lack of PM timer support, or else there's something >> broken. > > I'll reword that first sentence. > > OVMF doesn't look at the PM_TMR_BLK value when initializing that timer, > it only looks at the PCI host bridge device ID because OVMF is built > with QEMU in mind and there are only two possibles choices, QEMU is > running with a piix or q35 machine type, I think. We should split this statement in two. :) OVMF doesn't look at ACPI payload because it is a design goal to keep the guest firmware un-enlightened about such ACPI contents that arrive from the hypervisor. Parsing ACPI in firmware always looks attractive until someone actually writes the code, and then it always ends in misery -- at the latest when people realize they have to parse AML. Parsing ACPI is only feasible when you have a full-blown ACPICA (or similar) subsystem, and edk2 doesn't. Therefore, OVMF looks at either hardware, or specialized paravirt information channels such as fw_cfg files, that are easy to parse by design. Second, within the above design guidelines (i.e. "don't try to parse ACPI", and "cook your paravirt info if you want the firmware to eat it"), OVMF looks at such artifacts to steer its behavior for which patches have been submitted & merged. OVMF is integrated with Xen to the extent of patches merged from the Xen community. Thus, in my opinion, "OVMF is built with QEMU in mind" is a stretch -- perhaps it is so in *my* mind personally, but that's just me. We have designated reviewers for Xen-related code, and this series certainly builds OVMF with Xen in mind. :) If we reworded the statement, e.g. as "the present code targets QEMU and is unsuitable when running on Xen", then I would not object. Thanks! Laszlo >>> PVH and HVM. >>> >>> Note that the use of SecPeiDxeTimerLibCpu might be an issue with a >>> driver of type DXE_RUNTIME_DRIVER. I've attemptde to find out which of >> ^ attempted >>> the DXE_RUNTIME_DRIVER uses the TimerLib at runtime. I've done that by >>> replacing the TimerLib evaluation in >>> [LibraryClasses.common.DXE_RUNTIME_DRIVER] by a different one and >>> check every module that uses it (with the --report-file=report build >> ^ checking >>> option). >>> >>> ResetSystemRuntimeDxe is calling the TimerLib API at runtime to do the >>> operation "EfiResetCold", so this may never complete if the OS have >>> disabled the Local APIC Timer. >> >> Thanks, Roger. > > Thanks, > ___ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
Re: [Xen-devel] [PATCH v3 09/35] OvmfPkg/OvmfXen: use a TimerLib instance that depends only on the CPU
On Mon, Jul 15, 2019 at 04:22:19PM +0200, Roger Pau Monné wrote: > On Thu, Jul 04, 2019 at 03:42:07PM +0100, Anthony PERARD wrote: > > ACPI Timer does not work in a PVH guest, but local APIC works on both > > This is not accurate. It's not that the ACPI timer doesn't work, it's > just that it's not present. The PM_TMR_BLK should be set to 0 to > indicate the lack of PM timer support, or else there's something > broken. I'll reword that first sentence. OVMF doesn't look at the PM_TMR_BLK value when initializing that timer, it only looks at the PCI host bridge device ID because OVMF is built with QEMU in mind and there are only two possibles choices, QEMU is running with a piix or q35 machine type, I think. > > PVH and HVM. > > > > Note that the use of SecPeiDxeTimerLibCpu might be an issue with a > > driver of type DXE_RUNTIME_DRIVER. I've attemptde to find out which of > ^ attempted > > the DXE_RUNTIME_DRIVER uses the TimerLib at runtime. I've done that by > > replacing the TimerLib evaluation in > > [LibraryClasses.common.DXE_RUNTIME_DRIVER] by a different one and > > check every module that uses it (with the --report-file=report build > ^ checking > > option). > > > > ResetSystemRuntimeDxe is calling the TimerLib API at runtime to do the > > operation "EfiResetCold", so this may never complete if the OS have > > disabled the Local APIC Timer. > > Thanks, Roger. Thanks, -- Anthony PERARD ___ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
Re: [Xen-devel] [PATCH v3 09/35] OvmfPkg/OvmfXen: use a TimerLib instance that depends only on the CPU
On Thu, Jul 04, 2019 at 03:42:07PM +0100, Anthony PERARD wrote: > ACPI Timer does not work in a PVH guest, but local APIC works on both This is not accurate. It's not that the ACPI timer doesn't work, it's just that it's not present. The PM_TMR_BLK should be set to 0 to indicate the lack of PM timer support, or else there's something broken. > PVH and HVM. > > Note that the use of SecPeiDxeTimerLibCpu might be an issue with a > driver of type DXE_RUNTIME_DRIVER. I've attemptde to find out which of ^ attempted > the DXE_RUNTIME_DRIVER uses the TimerLib at runtime. I've done that by > replacing the TimerLib evaluation in > [LibraryClasses.common.DXE_RUNTIME_DRIVER] by a different one and > check every module that uses it (with the --report-file=report build ^ checking > option). > > ResetSystemRuntimeDxe is calling the TimerLib API at runtime to do the > operation "EfiResetCold", so this may never complete if the OS have > disabled the Local APIC Timer. Thanks, Roger. ___ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
Re: [Xen-devel] [PATCH v3 09/35] OvmfPkg/OvmfXen: use a TimerLib instance that depends only on the CPU
On 07/04/19 16:42, Anthony PERARD wrote: > ACPI Timer does not work in a PVH guest, but local APIC works on both > PVH and HVM. > > Note that the use of SecPeiDxeTimerLibCpu might be an issue with a > driver of type DXE_RUNTIME_DRIVER. I've attemptde to find out which of > the DXE_RUNTIME_DRIVER uses the TimerLib at runtime. I've done that by > replacing the TimerLib evaluation in > [LibraryClasses.common.DXE_RUNTIME_DRIVER] by a different one and > check every module that uses it (with the --report-file=report build > option). > > ResetSystemRuntimeDxe is calling the TimerLib API at runtime to do the > operation "EfiResetCold", so this may never complete if the OS have > disabled the Local APIC Timer. > > Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=1689 > Signed-off-by: Anthony PERARD > --- > > Notes: > v3: > - cleanup .dsc, leave only one TimerLib resolution > - Added a note in the commit message regarding the use of the local apic > by runtime drivers Good note -- yes, the warning in "MdePkg/Library/SecPeiDxeTimerLibCpu/SecPeiDxeTimerLibCpu.inf" applies. I guess Xen setups can live with that potential problem, for now. Acked-by: Laszlo Ersek Thanks Laszlo > > OvmfPkg/OvmfXen.dsc | 7 +-- > 1 file changed, 1 insertion(+), 6 deletions(-) > > diff --git a/OvmfPkg/OvmfXen.dsc b/OvmfPkg/OvmfXen.dsc > index 9f79d455fa..6288394eb8 100644 > --- a/OvmfPkg/OvmfXen.dsc > +++ b/OvmfPkg/OvmfXen.dsc > @@ -104,7 +104,7 @@ [SkuIds] > > > [LibraryClasses] >PcdLib|MdePkg/Library/BasePcdLibNull/BasePcdLibNull.inf > - TimerLib|OvmfPkg/Library/AcpiTimerLib/BaseAcpiTimerLib.inf > + TimerLib|MdePkg/Library/SecPeiDxeTimerLibCpu/SecPeiDxeTimerLibCpu.inf >PrintLib|MdePkg/Library/BasePrintLib/BasePrintLib.inf >BaseMemoryLib|MdePkg/Library/BaseMemoryLibRepStr/BaseMemoryLibRepStr.inf >BaseLib|MdePkg/Library/BaseLib/BaseLib.inf > @@ -202,7 +202,6 @@ [LibraryClasses.common] >BaseCryptLib|CryptoPkg/Library/BaseCryptLib/BaseCryptLib.inf > > [LibraryClasses.common.SEC] > - TimerLib|OvmfPkg/Library/AcpiTimerLib/BaseRomAcpiTimerLib.inf >QemuFwCfgLib|OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgSecLib.inf > !ifdef $(DEBUG_ON_SERIAL_PORT) >DebugLib|MdePkg/Library/BaseDebugLibSerialPort/BaseDebugLibSerialPort.inf > @@ -281,7 +280,6 @@ [LibraryClasses.common.DXE_CORE] > > [LibraryClasses.common.DXE_RUNTIME_DRIVER] >PcdLib|MdePkg/Library/DxePcdLib/DxePcdLib.inf > - TimerLib|OvmfPkg/Library/AcpiTimerLib/DxeAcpiTimerLib.inf >HobLib|MdePkg/Library/DxeHobLib/DxeHobLib.inf >DxeCoreEntryPoint|MdePkg/Library/DxeCoreEntryPoint/DxeCoreEntryPoint.inf > > MemoryAllocationLib|MdePkg/Library/UefiMemoryAllocationLib/UefiMemoryAllocationLib.inf > @@ -298,7 +296,6 @@ [LibraryClasses.common.DXE_RUNTIME_DRIVER] > > [LibraryClasses.common.UEFI_DRIVER] >PcdLib|MdePkg/Library/DxePcdLib/DxePcdLib.inf > - TimerLib|OvmfPkg/Library/AcpiTimerLib/DxeAcpiTimerLib.inf >HobLib|MdePkg/Library/DxeHobLib/DxeHobLib.inf >DxeCoreEntryPoint|MdePkg/Library/DxeCoreEntryPoint/DxeCoreEntryPoint.inf > > MemoryAllocationLib|MdePkg/Library/UefiMemoryAllocationLib/UefiMemoryAllocationLib.inf > @@ -313,7 +310,6 @@ [LibraryClasses.common.UEFI_DRIVER] > > [LibraryClasses.common.DXE_DRIVER] >PcdLib|MdePkg/Library/DxePcdLib/DxePcdLib.inf > - TimerLib|OvmfPkg/Library/AcpiTimerLib/DxeAcpiTimerLib.inf >HobLib|MdePkg/Library/DxeHobLib/DxeHobLib.inf > > MemoryAllocationLib|MdePkg/Library/UefiMemoryAllocationLib/UefiMemoryAllocationLib.inf > > ReportStatusCodeLib|MdeModulePkg/Library/DxeReportStatusCodeLib/DxeReportStatusCodeLib.inf > @@ -337,7 +333,6 @@ [LibraryClasses.common.DXE_DRIVER] > > [LibraryClasses.common.UEFI_APPLICATION] >PcdLib|MdePkg/Library/DxePcdLib/DxePcdLib.inf > - TimerLib|OvmfPkg/Library/AcpiTimerLib/DxeAcpiTimerLib.inf >HobLib|MdePkg/Library/DxeHobLib/DxeHobLib.inf > > MemoryAllocationLib|MdePkg/Library/UefiMemoryAllocationLib/UefiMemoryAllocationLib.inf > > ReportStatusCodeLib|MdeModulePkg/Library/DxeReportStatusCodeLib/DxeReportStatusCodeLib.inf > ___ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
[Xen-devel] [PATCH v3 09/35] OvmfPkg/OvmfXen: use a TimerLib instance that depends only on the CPU
ACPI Timer does not work in a PVH guest, but local APIC works on both PVH and HVM. Note that the use of SecPeiDxeTimerLibCpu might be an issue with a driver of type DXE_RUNTIME_DRIVER. I've attemptde to find out which of the DXE_RUNTIME_DRIVER uses the TimerLib at runtime. I've done that by replacing the TimerLib evaluation in [LibraryClasses.common.DXE_RUNTIME_DRIVER] by a different one and check every module that uses it (with the --report-file=report build option). ResetSystemRuntimeDxe is calling the TimerLib API at runtime to do the operation "EfiResetCold", so this may never complete if the OS have disabled the Local APIC Timer. Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=1689 Signed-off-by: Anthony PERARD --- Notes: v3: - cleanup .dsc, leave only one TimerLib resolution - Added a note in the commit message regarding the use of the local apic by runtime drivers OvmfPkg/OvmfXen.dsc | 7 +-- 1 file changed, 1 insertion(+), 6 deletions(-) diff --git a/OvmfPkg/OvmfXen.dsc b/OvmfPkg/OvmfXen.dsc index 9f79d455fa..6288394eb8 100644 --- a/OvmfPkg/OvmfXen.dsc +++ b/OvmfPkg/OvmfXen.dsc @@ -104,7 +104,7 @@ [SkuIds] [LibraryClasses] PcdLib|MdePkg/Library/BasePcdLibNull/BasePcdLibNull.inf - TimerLib|OvmfPkg/Library/AcpiTimerLib/BaseAcpiTimerLib.inf + TimerLib|MdePkg/Library/SecPeiDxeTimerLibCpu/SecPeiDxeTimerLibCpu.inf PrintLib|MdePkg/Library/BasePrintLib/BasePrintLib.inf BaseMemoryLib|MdePkg/Library/BaseMemoryLibRepStr/BaseMemoryLibRepStr.inf BaseLib|MdePkg/Library/BaseLib/BaseLib.inf @@ -202,7 +202,6 @@ [LibraryClasses.common] BaseCryptLib|CryptoPkg/Library/BaseCryptLib/BaseCryptLib.inf [LibraryClasses.common.SEC] - TimerLib|OvmfPkg/Library/AcpiTimerLib/BaseRomAcpiTimerLib.inf QemuFwCfgLib|OvmfPkg/Library/QemuFwCfgLib/QemuFwCfgSecLib.inf !ifdef $(DEBUG_ON_SERIAL_PORT) DebugLib|MdePkg/Library/BaseDebugLibSerialPort/BaseDebugLibSerialPort.inf @@ -281,7 +280,6 @@ [LibraryClasses.common.DXE_CORE] [LibraryClasses.common.DXE_RUNTIME_DRIVER] PcdLib|MdePkg/Library/DxePcdLib/DxePcdLib.inf - TimerLib|OvmfPkg/Library/AcpiTimerLib/DxeAcpiTimerLib.inf HobLib|MdePkg/Library/DxeHobLib/DxeHobLib.inf DxeCoreEntryPoint|MdePkg/Library/DxeCoreEntryPoint/DxeCoreEntryPoint.inf MemoryAllocationLib|MdePkg/Library/UefiMemoryAllocationLib/UefiMemoryAllocationLib.inf @@ -298,7 +296,6 @@ [LibraryClasses.common.DXE_RUNTIME_DRIVER] [LibraryClasses.common.UEFI_DRIVER] PcdLib|MdePkg/Library/DxePcdLib/DxePcdLib.inf - TimerLib|OvmfPkg/Library/AcpiTimerLib/DxeAcpiTimerLib.inf HobLib|MdePkg/Library/DxeHobLib/DxeHobLib.inf DxeCoreEntryPoint|MdePkg/Library/DxeCoreEntryPoint/DxeCoreEntryPoint.inf MemoryAllocationLib|MdePkg/Library/UefiMemoryAllocationLib/UefiMemoryAllocationLib.inf @@ -313,7 +310,6 @@ [LibraryClasses.common.UEFI_DRIVER] [LibraryClasses.common.DXE_DRIVER] PcdLib|MdePkg/Library/DxePcdLib/DxePcdLib.inf - TimerLib|OvmfPkg/Library/AcpiTimerLib/DxeAcpiTimerLib.inf HobLib|MdePkg/Library/DxeHobLib/DxeHobLib.inf MemoryAllocationLib|MdePkg/Library/UefiMemoryAllocationLib/UefiMemoryAllocationLib.inf ReportStatusCodeLib|MdeModulePkg/Library/DxeReportStatusCodeLib/DxeReportStatusCodeLib.inf @@ -337,7 +333,6 @@ [LibraryClasses.common.DXE_DRIVER] [LibraryClasses.common.UEFI_APPLICATION] PcdLib|MdePkg/Library/DxePcdLib/DxePcdLib.inf - TimerLib|OvmfPkg/Library/AcpiTimerLib/DxeAcpiTimerLib.inf HobLib|MdePkg/Library/DxeHobLib/DxeHobLib.inf MemoryAllocationLib|MdePkg/Library/UefiMemoryAllocationLib/UefiMemoryAllocationLib.inf ReportStatusCodeLib|MdeModulePkg/Library/DxeReportStatusCodeLib/DxeReportStatusCodeLib.inf -- Anthony PERARD ___ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
