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KVM: SEV: Automatically switch reclaimed pages to shared

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Currently there's a consistent pattern of always calling
host_rmp_make_shared() immediately after snp_page_reclaim(), so go ahead
and handle it automatically as part of snp_page_reclaim(). Also rename
it to kvm_rmp_make_shared() to more easily distinguish it as a
KVM-specific variant of the more generic rmp_make_shared() helper.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Michael Roth <michael.roth@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Michael Roth 2024-05-28 15:58:09 -05:00 committed by Paolo Bonzini
parent 6f627b4253
commit febff040b1
1 changed files with 31 additions and 24 deletions
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55
arch/x86/kvm/svm/sev.c
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@ -262,6 +262,21 @@ static void sev_decommission(unsigned int handle)
sev_guest_decommission(&decommission, NULL);
}
/*
* Transition a page to hypervisor-owned/shared state in the RMP table. This
* should not fail under normal conditions, but leak the page should that
* happen since it will no longer be usable by the host due to RMP protections.
*/
static int kvm_rmp_make_shared(struct kvm *kvm, u64 pfn, enum pg_level level)
{
if (KVM_BUG_ON(rmp_make_shared(pfn, level), kvm)) {
snp_leak_pages(pfn, page_level_size(level) >> PAGE_SHIFT);
return -EIO;
}
return 0;
}
/*
* Certain page-states, such as Pre-Guest and Firmware pages (as documented
* in Chapter 5 of the SEV-SNP Firmware ABI under "Page States") cannot be
@ -271,32 +286,25 @@ static void sev_decommission(unsigned int handle)
* Until they are reclaimed and subsequently transitioned via RMPUPDATE, they
* might not be usable by the host due to being set as immutable or still
* being associated with a guest ASID.
*
* Bug the VM and leak the page if reclaim fails, or if the RMP entry can't be
* converted back to shared, as the page is no longer usable due to RMP
* protections, and it's infeasible for the guest to continue on.
*/
static int snp_page_reclaim(u64 pfn)
static int snp_page_reclaim(struct kvm *kvm, u64 pfn)
{
struct sev_data_snp_page_reclaim data = {0};
int err, rc;
int fw_err, rc;
data.paddr = __sme_set(pfn << PAGE_SHIFT);
rc = sev_do_cmd(SEV_CMD_SNP_PAGE_RECLAIM, &data, &err);
if (WARN_ONCE(rc, "Failed to reclaim PFN %llx", pfn))
rc = sev_do_cmd(SEV_CMD_SNP_PAGE_RECLAIM, &data, &fw_err);
if (KVM_BUG(rc, kvm, "Failed to reclaim PFN %llx, rc %d fw_err %d", pfn, rc, fw_err)) {
snp_leak_pages(pfn, 1);
return -EIO;
}
return rc;
}
/*
* Transition a page to hypervisor-owned/shared state in the RMP table. This
* should not fail under normal conditions, but leak the page should that
* happen since it will no longer be usable by the host due to RMP protections.
*/
static int host_rmp_make_shared(u64 pfn, enum pg_level level)
{
int rc;
rc = rmp_make_shared(pfn, level);
if (WARN_ON_ONCE(rc))
snp_leak_pages(pfn, page_level_size(level) >> PAGE_SHIFT);
if (kvm_rmp_make_shared(kvm, pfn, PG_LEVEL_4K))
return -EIO;
return rc;
}
@ -2244,7 +2252,7 @@ fw_err:
* information to provide information on which CPUID leaves/fields
* failed CPUID validation.
*/
if (!snp_page_reclaim(pfn + i) && !host_rmp_make_shared(pfn + i, PG_LEVEL_4K) &&
if (!snp_page_reclaim(kvm, pfn + i) &&
sev_populate_args->type == KVM_SEV_SNP_PAGE_TYPE_CPUID &&
sev_populate_args->fw_error == SEV_RET_INVALID_PARAM) {
void *vaddr = kmap_local_pfn(pfn + i);
@ -2262,7 +2270,7 @@ err:
pr_debug("%s: exiting with error ret %d (fw_error %d), restoring %d gmem PFNs to shared.\n",
__func__, ret, sev_populate_args->fw_error, n_private);
for (i = 0; i < n_private; i++)
host_rmp_make_shared(pfn + i, PG_LEVEL_4K);
kvm_rmp_make_shared(kvm, pfn + i, PG_LEVEL_4K);
return ret;
}
@ -2380,8 +2388,7 @@ static int snp_launch_update_vmsa(struct kvm *kvm, struct kvm_sev_cmd *argp)
ret = __sev_issue_cmd(argp->sev_fd, SEV_CMD_SNP_LAUNCH_UPDATE,
&data, &argp->error);
if (ret) {
if (!snp_page_reclaim(pfn))
host_rmp_make_shared(pfn, PG_LEVEL_4K);
snp_page_reclaim(kvm, pfn);
return ret;
}
@ -3069,7 +3076,7 @@ void sev_free_vcpu(struct kvm_vcpu *vcpu)
if (sev_snp_guest(vcpu->kvm)) {
u64 pfn = __pa(svm->sev_es.vmsa) >> PAGE_SHIFT;
if (host_rmp_make_shared(pfn, PG_LEVEL_4K))
if (kvm_rmp_make_shared(vcpu->kvm, pfn, PG_LEVEL_4K))
goto skip_vmsa_free;
}