Re: [PATCH v2 14/14] KVM: SVM: Skip SEV cache flush if no ASIDs have been used

Paolo Bonzini
2021-01-28T15:12:55Z

On 14/01/21 01:37, Sean Christopherson wrote:
> Skip SEV's expensive WBINVD and DF_FLUSH if there are no SEV ASIDs
> waiting to be reclaimed, e.g. if SEV was never used. This "fixes" an
> issue where the DF_FLUSH fails during hardware teardown if the original
> SEV_INIT failed. Ideally, SEV wouldn't be marked as enabled in KVM if
> SEV_INIT fails, but that's a problem for another day.
>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
> arch/x86/kvm/svm/sev.c | 22 ++++++++++------------
> 1 file changed, 10 insertions(+), 12 deletions(-)
>
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 23a4bead4a82..e71bc742d8da 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -56,9 +56,14 @@ struct enc_region {
> unsigned long size;
> };
>
> -static int sev_flush_asids(void)
> +static int sev_flush_asids(int min_asid, int max_asid)
> {
> - int ret, error = 0;
> + int ret, pos, error = 0;
> +
> + /* Check if there are any ASIDs to reclaim before performing a flush */
> + pos = find_next_bit(sev_reclaim_asid_bitmap, max_sev_asid, min_asid);
> + if (pos >= max_asid)
> + return -EBUSY;
>
> /*
> * DEACTIVATE will clear the WBINVD indicator causing DF_FLUSH to fail,
> @@ -80,14 +85,7 @@ static int sev_flush_asids(void)
> /* Must be called with the sev_bitmap_lock held */
> static bool __sev_recycle_asids(int min_asid, int max_asid)
> {
> - int pos;
> -
> - /* Check if there are any ASIDs to reclaim before performing a flush */
> - pos = find_next_bit(sev_reclaim_asid_bitmap, max_sev_asid, min_asid);
> - if (pos >= max_asid)
> - return false;
> -
> - if (sev_flush_asids())
> + if (sev_flush_asids(min_asid, max_asid))
> return false;
>
> /* The flush process will flush all reclaimable SEV and SEV-ES ASIDs */
> @@ -1323,10 +1321,10 @@ void sev_hardware_teardown(void)
> if (!sev_enabled)
> return;
>
> + sev_flush_asids(0, max_sev_asid);
> +
> bitmap_free(sev_asid_bitmap);
> bitmap_free(sev_reclaim_asid_bitmap);
> -
> - sev_flush_asids();
> }
>
> int sev_cpu_init(struct svm_cpu_data *sd)
>

I can't find 00/14 in my inbox, so: queued 1-3 and 6-14, thanks.

Paolo