Comments below: From: Laszlo Ersek [mailto:ler...@redhat.com] Sent: Wednesday, November 30, 2016 5:54 AM To: Yao, Jiewen <jiewen....@intel.com>; edk2-de...@ml01.01.org Cc: Kinney, Michael D <michael.d.kin...@intel.com>; Fan, Jeff <jeff....@intel.com> Subject: Re: [edk2] [PATCH] UefiCpuPkg:PiSmmCpu: Set correct attribute on split.
On 11/29/16 08:39, Jiewen Yao wrote: > PiSmmCpu driver may split page for page attribute request. > Current logic will propagate the super page attribute attribute. > However, it might be wrong because we cannot clear protection > without touch super page attribute. > > We should always clear protection on super page and set > protection on end page for easy clear later. > > Cc: Jeff Fan <jeff....@intel.com<mailto:jeff....@intel.com>> > Cc: Michael D Kinney > <michael.d.kin...@intel.com<mailto:michael.d.kin...@intel.com>> > Cc: Laszlo Ersek <ler...@redhat.com<mailto:ler...@redhat.com>> > Contributed-under: TianoCore Contribution Agreement 1.0 > Signed-off-by: Jiewen Yao <jiewen....@intel.com<mailto:jiewen....@intel.com>> > --- > UefiCpuPkg/PiSmmCpuDxeSmm/SmmCpuMemoryManagement.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/UefiCpuPkg/PiSmmCpuDxeSmm/SmmCpuMemoryManagement.c > b/UefiCpuPkg/PiSmmCpuDxeSmm/SmmCpuMemoryManagement.c > index accc11e..d0f41a8 100644 > --- a/UefiCpuPkg/PiSmmCpuDxeSmm/SmmCpuMemoryManagement.c > +++ b/UefiCpuPkg/PiSmmCpuDxeSmm/SmmCpuMemoryManagement.c > @@ -303,7 +303,7 @@ SplitPage ( > for (Index = 0; Index < SIZE_4KB / sizeof(UINT64); Index++) { > NewPageEntry[Index] = BaseAddress + SIZE_4KB * Index + ((*PageEntry) > & PAGE_PROGATE_BITS); > } > - (*PageEntry) = (UINT64)(UINTN)NewPageEntry + ((*PageEntry) & > PAGE_PROGATE_BITS); > + (*PageEntry) = (UINT64)(UINTN)NewPageEntry + PAGE_ATTRIBUTE_BITS; > return RETURN_SUCCESS; > } else { > return RETURN_UNSUPPORTED; > @@ -324,7 +324,7 @@ SplitPage ( > for (Index = 0; Index < SIZE_4KB / sizeof(UINT64); Index++) { > NewPageEntry[Index] = BaseAddress + SIZE_2MB * Index + IA32_PG_PS + > ((*PageEntry) & PAGE_PROGATE_BITS); > } > - (*PageEntry) = (UINT64)(UINTN)NewPageEntry + ((*PageEntry) & > PAGE_PROGATE_BITS); > + (*PageEntry) = (UINT64)(UINTN)NewPageEntry + PAGE_ATTRIBUTE_BITS; > return RETURN_SUCCESS; > } else { > return RETURN_UNSUPPORTED; > I had to stare a while at this, to get a superficial understanding :) But, it does seem to make sense (I checked PAGE_ATTRIBUTE_BITS and PAGE_PROGATE_BITS too, just to be sure). So, this change preserves the protection inheritance for the leaf pages, but clears NX and sets Dirty / Accessed / Writeable / Present on the relevant parent entry. (I see hat User mode access is enabled as well; I don't know why that is useful here.) [Jiewen] Yes. You are right. Some notes about the commit message: - we have "attribute attribute". I think we should either drop one of those words, or say "super page attribute to leaf page attribute". [Jiewen] Agree. I will update. - "end page" might be more clearly stated as "leaf page" (just a guess) [Jiewen] Agree. I will update. - I think it would be useful to mention, for the uninitiated like me :), that the effective protection is (apparently) the strictest combination across the levels. [Jiewen] Agree. I will update. - What do you think of the following subject line? UefiCpuPkg/PiSmmCpuDxeSmm: relax superpage protection on page split [Jiewen] Agree. I will update. Anyway, to the extent that I understand this, I agree: Acked-by: Laszlo Ersek <ler...@redhat.com<mailto:ler...@redhat.com>> I gave the patch a bit of testing in my usual environment; it seems to cause no problems. [Jiewen] Thank you. Tested-by: Laszlo Ersek <ler...@redhat.com<mailto:ler...@redhat.com>> Thanks Laszlo _______________________________________________ edk2-devel mailing list edk2-devel@lists.01.org https://lists.01.org/mailman/listinfo/edk2-devel
