Re: [PATCH] arm64: tegra: only map accessible sysram
On 9/30/19 4:02 AM, Mian Yousaf Kaukab wrote: On Sun, Sep 29, 2019 at 11:28:43PM -0600, Stephen Warren wrote: On 9/29/19 2:08 PM, Mian Yousaf Kaukab wrote: Most of the SysRAM is secure and only accessible by TF-A. Don't map this inaccessible memory in kernel. Only map pages used by bpmp driver. I don't believe this change is correct. The actual patch doesn't implement mapping a subset of the RAM (a software issue), but rather it changes the DT representation of the SYSRAM hardware. The SYSRAM hardware always does start at 0x3000, even if a subset of the address range is dedicated to a specific purpose. If the kernel must map only part of the RAM, then some additional property should indicate this.[...] I agree the hardware description becomes inaccurate with this change. In the current setup complete 0x3000_ to 0x3005_ range is being mapped as normal memory (MT_NORMAL_NC). Though only 0x3004_E000 to 0x3005_ are accessible by the kernel. Nit: I expect that a much larger region than that is *accessible*, although it's quite plausible that only that region is actually *accessed*/used right now. I am seeing an issue where a read access (which I believe is speculative) to inaccessible range causes an SError. Another solution for this problem could be to add "no-memory-wc" to SysRAM node so that it is mapped as device memory (MT_DEVICE_nGnRE). Would that be acceptable? Why does the driver blindly map the entire memory at all? Surely it should only map the portions of RAM that other drivers request/use? And surely the BPMP driver or DT node is already providing that information? But yes, changing the mapping type to avoid speculation might be an acceptable solution for now, although I think we'd want to work things out better later. I don't know if there would be any impact to the BPMP driver related to the slower SRAM access due to this change. Best consult a BPMP expert or Tegra maintainer about that. [...] Also, I believe it's incorrect to hard-code into the kernel's DT the range of addresses used by the secure monitor/OS, since this can vary depending on what the user actually chooses to install as the secure monitor/OS. Any indication of such regions should be filled in at runtime by some boot firmware or the secure monitor/OS itself, or retrieved using some runtime API rather than DT. Secure-OS addresses are not of interest here. SysRAM is partitioned between secure-OS and BPMP and kernel is only interested in the BPMP part. The firmware can update these addresses in the device-tree if it wants to. Would you prefer something similar implemented in u-boot so that it updates SysRAM node to only expose kernel accessible part of it to the kernel? Can u-boot dynamically figure out the Secure-OS vs BPMP partition? BR, Yousaf
Re: [PATCH] arm64: tegra: only map accessible sysram
On Sun, Sep 29, 2019 at 11:28:43PM -0600, Stephen Warren wrote: > On 9/29/19 2:08 PM, Mian Yousaf Kaukab wrote: > > Most of the SysRAM is secure and only accessible by TF-A. > > Don't map this inaccessible memory in kernel. Only map pages > > used by bpmp driver. > > I don't believe this change is correct. The actual patch doesn't > implement mapping a subset of the RAM (a software issue), but rather it > changes the DT representation of the SYSRAM hardware. The SYSRAM > hardware always does start at 0x3000, even if a subset of the > address range is dedicated to a specific purpose. If the kernel must map > only part of the RAM, then some additional property should indicate > this.[...] I agree the hardware description becomes inaccurate with this change. In the current setup complete 0x3000_ to 0x3005_ range is being mapped as normal memory (MT_NORMAL_NC). Though only 0x3004_E000 to 0x3005_ are accessible by the kernel. I am seeing an issue where a read access (which I believe is speculative) to inaccessible range causes an SError. Another solution for this problem could be to add "no-memory-wc" to SysRAM node so that it is mapped as device memory (MT_DEVICE_nGnRE). Would that be acceptable? > [...] Also, I believe it's incorrect to hard-code into the kernel's DT > the range of addresses used by the secure monitor/OS, since this can > vary depending on what the user actually chooses to install as the > secure monitor/OS. Any indication of such regions should be filled in at > runtime by some boot firmware or the secure monitor/OS itself, or > retrieved using some runtime API rather than DT. Secure-OS addresses are not of interest here. SysRAM is partitioned between secure-OS and BPMP and kernel is only interested in the BPMP part. The firmware can update these addresses in the device-tree if it wants to. Would you prefer something similar implemented in u-boot so that it updates SysRAM node to only expose kernel accessible part of it to the kernel? Can u-boot dynamically figure out the Secure-OS vs BPMP partition? BR, Yousaf
Re: [PATCH] arm64: tegra: only map accessible sysram
On 9/29/19 2:08 PM, Mian Yousaf Kaukab wrote: > Most of the SysRAM is secure and only accessible by TF-A. > Don't map this inaccessible memory in kernel. Only map pages > used by bpmp driver. I don't believe this change is correct. The actual patch doesn't implement mapping a subset of the RAM (a software issue), but rather it changes the DT representation of the SYSRAM hardware. The SYSRAM hardware always does start at 0x3000, even if a subset of the address range is dedicated to a specific purpose. If the kernel must map only part of the RAM, then some additional property should indicate this. Also, I believe it's incorrect to hard-code into the kernel's DT the range of addresses used by the secure monitor/OS, since this can vary depending on what the user actually chooses to install as the secure monitor/OS. Any indication of such regions should be filled in at runtime by some boot firmware or the secure monitor/OS itself, or retrieved using some runtime API rather than DT.
[PATCH] arm64: tegra: only map accessible sysram
Most of the SysRAM is secure and only accessible by TF-A.
Don't map this inaccessible memory in kernel. Only map pages
used by bpmp driver.
Signed-off-by: Mian Yousaf Kaukab
---
Only tegra186 is tested. Tested on Jetson TX2.
arch/arm64/boot/dts/nvidia/tegra186.dtsi | 14 +++---
arch/arm64/boot/dts/nvidia/tegra194.dtsi | 14 +++---
2 files changed, 14 insertions(+), 14 deletions(-)
diff --git a/arch/arm64/boot/dts/nvidia/tegra186.dtsi
b/arch/arm64/boot/dts/nvidia/tegra186.dtsi
index 47cd831fcf44..a861f46125fd 100644
--- a/arch/arm64/boot/dts/nvidia/tegra186.dtsi
+++ b/arch/arm64/boot/dts/nvidia/tegra186.dtsi
@@ -1174,23 +1174,23 @@
power-domains = < TEGRA186_POWER_DOMAIN_GPU>;
};
- sysram@3000 {
+ sysram@3004e000 {
compatible = "nvidia,tegra186-sysram", "mmio-sram";
- reg = <0x0 0x3000 0x0 0x5>;
+ reg = <0x0 0x3004e000 0x0 0x2000>;
#address-cells = <2>;
#size-cells = <2>;
- ranges = <0 0x0 0x0 0x3000 0x0 0x5>;
+ ranges = <0 0x0 0x0 0x3004e000 0x0 0x2000>;
- cpu_bpmp_tx: shmem@4e000 {
+ cpu_bpmp_tx: shmem@e000 {
compatible = "nvidia,tegra186-bpmp-shmem";
- reg = <0x0 0x4e000 0x0 0x1000>;
+ reg = <0x0 0x0 0x0 0x1000>;
label = "cpu-bpmp-tx";
pool;
};
- cpu_bpmp_rx: shmem@4f000 {
+ cpu_bpmp_rx: shmem@f000 {
compatible = "nvidia,tegra186-bpmp-shmem";
- reg = <0x0 0x4f000 0x0 0x1000>;
+ reg = <0x0 0x1000 0x0 0x1000>;
label = "cpu-bpmp-rx";
pool;
};
diff --git a/arch/arm64/boot/dts/nvidia/tegra194.dtsi
b/arch/arm64/boot/dts/nvidia/tegra194.dtsi
index 3c0cf54f0aab..98b9399d6b7f 100644
--- a/arch/arm64/boot/dts/nvidia/tegra194.dtsi
+++ b/arch/arm64/boot/dts/nvidia/tegra194.dtsi
@@ -1430,23 +1430,23 @@
0x8200 0x0 0x4000 0x1f 0x4000 0x0
0xc000>; /* non-prefetchable memory (3GB) */
};
- sysram@4000 {
+ sysram@4004e000 {
compatible = "nvidia,tegra194-sysram", "mmio-sram";
- reg = <0x0 0x4000 0x0 0x5>;
+ reg = <0x0 0x4004e000 0x0 0x2000>;
#address-cells = <1>;
#size-cells = <1>;
- ranges = <0x0 0x0 0x4000 0x5>;
+ ranges = <0x0 0x0 0x4004e000 0x2000>;
- cpu_bpmp_tx: shmem@4e000 {
+ cpu_bpmp_tx: shmem@e000 {
compatible = "nvidia,tegra194-bpmp-shmem";
- reg = <0x4e000 0x1000>;
+ reg = <0x0 0x1000>;
label = "cpu-bpmp-tx";
pool;
};
- cpu_bpmp_rx: shmem@4f000 {
+ cpu_bpmp_rx: shmem@f000 {
compatible = "nvidia,tegra194-bpmp-shmem";
- reg = <0x4f000 0x1000>;
+ reg = <0x1000 0x1000>;
label = "cpu-bpmp-rx";
pool;
};
--
2.16.4
