On Tue, Oct 01, 2024, Suravee Suthikulpanit wrote: > Hi Sean, > > On 9/30/2024 11:04 PM, Sean Christopherson wrote: > > On Mon, Sep 30, 2024, Suravee Suthikulpanit wrote: > > > On SNP-enabled system, VMRUN marks AVIC Backing Page as in-use while > > > the guest is running for both secure and non-secure guest. This causes > > > any attempts to modify the RMP entries for the backing page to result in > > > FAIL_INUSE response. This is to ensure that the AVIC backing page is not > > > maliciously assigned to an SNP guest while the unencrypted guest is active. > > > > > > Currently, an attempt to run AVIC guest would result in the following error: > > > > > > BUG: unable to handle page fault for address: ff3a442e549cc270 > > > #PF: supervisor write access in kernel mode > > > #PF: error_code(0x80000003) - RMP violation > > > PGD b6ee01067 P4D b6ee02067 PUD 10096d063 PMD 11c540063 PTE 80000001149cc163 > > > SEV-SNP: PFN 0x1149cc unassigned, dumping non-zero entries in 2M PFN region: [0x114800 - 0x114a00] > > > ... > > This should be "fixed" by commit 75253db41a46 ("KVM: SEV: Make AVIC backing, VMSA > > and VMCB memory allocation SNP safe"), no? > > The commit 75253db41a46 fixes another issue related to 2MB-aligned in-use > page, where the CPU incorrectly treats the whole 2MB region as in-use and > signal an RMP violation #PF. > > This enhancement is mainly to allow hypervisor to write to the AVIC backing > page of non-secure guest on SNP-enabled system. In that case, the changelog needs to be rewritten, because the changelog very explicitly talks about modifying RMP entries, whereas IIUC, the issue is that cross-CPU writes to a vCPU's vAPIC page, e.g. to inject an interrupt, will generate unexpected #PFs in the host. > Note: This change might need to be ported to stable 6.9, 6.10, and 6.11 tree > as well. At the very least, it needs a fixes, which I believe is: Fixes: 216d106c7ff7 ("x86/sev: Add SEV-SNP host initialization support") 6.9 and 6.10 aren't LTS kernels, so backports to them aren't necessary.