On 3/20/24 09:39, Michael Roth wrote:
SEV uses these notifiers to register/pin pages prior to guest use, since they could potentially be used for private memory where page migration is not supported. But SNP only uses guest_memfd-provided pages for private memory, which has its own kernel-internal mechanisms for registering/pinning memory. Signed-off-by: Michael Roth <michael.roth@xxxxxxx> --- target/i386/sev.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) diff --git a/target/i386/sev.c b/target/i386/sev.c index 61af312a11..774262d834 100644 --- a/target/i386/sev.c +++ b/target/i386/sev.c @@ -982,7 +982,15 @@ static int sev_kvm_init(ConfidentialGuestSupport *cgs, Error **errp) goto err; }- ram_block_notifier_add(&sev_ram_notifier);+ if (!sev_snp_enabled()) { + /* + * SEV uses these notifiers to register/pin pages prior to guest use, + * but SNP relies on guest_memfd for private pages, which has it's + * own internal mechanisms for registering/pinning private memory. + */ + ram_block_notifier_add(&sev_ram_notifier); + } + qemu_add_machine_init_done_notifier(&sev_machine_done_notify); qemu_add_vm_change_state_handler(sev_vm_state_change, sev_common);
These three lines can be done in any order, so I suggest removing ram_block_notifier_add + qemu_add_machine_init_done_notifier from the sev-common implementation of kvm_init (let's call it sev_common_kvm_init); and add an override in sev-guest that calls them if sev_common_kvm_init() succeeds.
(treat this as a review for 25/26/29). Paolo
