On 10/9/20 1:58 AM, Sean Christopherson wrote: > On Thu, Oct 08, 2020 at 03:54:12PM +0800, yulei.kernel@xxxxxxxxx wrote: >> From: Yulei Zhang <yuleixzhang@xxxxxxxxxxx> >> >> Dmem page is pfn invalid but not mmio. Support cacheable >> dmem page for kvm. >> >> Signed-off-by: Chen Zhuo <sagazchen@xxxxxxxxxxx> >> Signed-off-by: Yulei Zhang <yuleixzhang@xxxxxxxxxxx> >> --- >> arch/x86/kvm/mmu/mmu.c | 5 +++-- >> include/linux/dmem.h | 7 +++++++ >> mm/dmem.c | 7 +++++++ >> 3 files changed, 17 insertions(+), 2 deletions(-) >> >> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c >> index 71aa3da2a0b7..0115c1767063 100644 >> --- a/arch/x86/kvm/mmu/mmu.c >> +++ b/arch/x86/kvm/mmu/mmu.c >> @@ -41,6 +41,7 @@ >> #include <linux/hash.h> >> #include <linux/kern_levels.h> >> #include <linux/kthread.h> >> +#include <linux/dmem.h> >> >> #include <asm/page.h> >> #include <asm/memtype.h> >> @@ -2962,9 +2963,9 @@ static bool kvm_is_mmio_pfn(kvm_pfn_t pfn) >> */ >> (!pat_enabled() || pat_pfn_immune_to_uc_mtrr(pfn)); >> >> - return !e820__mapped_raw_any(pfn_to_hpa(pfn), >> + return (!e820__mapped_raw_any(pfn_to_hpa(pfn), >> pfn_to_hpa(pfn + 1) - 1, >> - E820_TYPE_RAM); >> + E820_TYPE_RAM)) || (!is_dmem_pfn(pfn)); > > This is wrong. As is, the logic reads "A PFN is MMIO if it is INVALID && > (!RAM || !DMEM)". The obvious fix would be to change it to "INVALID && > !RAM && !DMEM", but that begs the question of whether or DMEM is reported > as RAM. I don't see any e820 related changes in the series, i.e. no evidence > that dmem yanks its memory out of the e820 tables, which makes me think this > change is unnecessary. > Even if there would exist e820 changes, e820__mapped_raw_any() checks against hardware-provided e820 that we are given before any changes happen i.e. not the one kernel has changed (e820_table_firmware). So unless you're having that memory carved from an MMIO range (which would be wrong), or the BIOS is misrepresenting its memory map... the e820__mapped_raw_any(E820_TYPE_RAM) ought to be enough to cover RAM. Or at least that has been my experience with similar work. Joao
