> From: Zhao, Yan Y <yan.y.zhao@xxxxxxxxx> > Sent: Tuesday, May 7, 2024 2:20 PM > @@ -101,9 +101,21 @@ static bool kvm_is_mmio_pfn(kvm_pfn_t pfn) > */ > (!pat_enabled() || > pat_pfn_immune_to_uc_mtrr(pfn)); > > + /* > + * If the PFN is invalid and not RAM in raw e820 table, keep treating it > + * as MMIO. > + * > + * If the PFN is invalid and is RAM in raw e820 table, > + * - if PAT is not enabled, always treat the PFN as MMIO to avoid > futher > + * checking of MTRRs. > + * - if PAT is enabled, treat the PFN as MMIO if its PAT is UC/WC/UC- > in > + * primary MMU. > + * to prevent guest cacheable access to MMIO PFNs. > + */ > return !e820__mapped_raw_any(pfn_to_hpa(pfn), > pfn_to_hpa(pfn + 1) - 1, > - E820_TYPE_RAM); > + E820_TYPE_RAM) ? true : > + (!pat_enabled() || > pat_pfn_immune_to_uc_mtrr(pfn)); Is it for another theoretical problem in case the primary mmu uses a non-WB type on a invalid RAM-type pfn so you want to do additional scrutiny here?
