lkml.org 
[lkml]   [2021]   [Jul]   [29]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    SubjectRe: [PATCH v2 01/13] KVM: s390: pv: avoid stall notifications for some UVCs
    Date
    On 7/28/21 4:26 PM, Claudio Imbrenda wrote:
    > Improve make_secure_pte to avoid stalls when the system is heavily
    > overcommitted. This was especially problematic in kvm_s390_pv_unpack,
    > because of the loop over all pages that needed unpacking.
    >
    > Also fix kvm_s390_pv_init_vm to avoid stalls when the system is heavily
    > overcommitted.

    Fixes tag?

    >
    > Signed-off-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
    > ---
    > arch/s390/kernel/uv.c | 11 ++++++++---
    > arch/s390/kvm/pv.c | 2 +-
    > 2 files changed, 9 insertions(+), 4 deletions(-)
    >
    > diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c
    > index aeb0a15bcbb7..fd0faa51c1bb 100644
    > --- a/arch/s390/kernel/uv.c
    > +++ b/arch/s390/kernel/uv.c
    > @@ -196,11 +196,16 @@ static int make_secure_pte(pte_t *ptep, unsigned long addr,
    > if (!page_ref_freeze(page, expected))
    > return -EBUSY;
    > set_bit(PG_arch_1, &page->flags);
    > - rc = uv_call(0, (u64)uvcb);
    > + rc = __uv_call(0, (u64)uvcb);

    We should exchange rc with cc since that's what we get back from
    __uv_call(). Technically we always get a cc but for the other functions
    it's only ever 0/1 which translates to success/error so rc is ok.

    > page_ref_unfreeze(page, expected);
    > - /* Return -ENXIO if the page was not mapped, -EINVAL otherwise */
    > - if (rc)
    > + /*
    > + * Return -ENXIO if the page was not mapped, -EINVAL for other errors.
    > + * If busy or partially completed, return -EAGAIN.
    > + */
    > + if (rc == 1)
    > rc = uvcb->rc == 0x10a ? -ENXIO : -EINVAL;
    > + else if (rc > 1)
    > + rc = -EAGAIN;
    > return rc;

    Could you define the CCs in uv.h and check against the constants here so
    it's easier to understand that the rc > 1 checks against a "UV was busy
    please re-issue the call again" cc?

    Maybe also make it explicit for cc 2 and 3 instead of cc > 1

    > }
    >
    > diff --git a/arch/s390/kvm/pv.c b/arch/s390/kvm/pv.c
    > index c8841f476e91..e007df11a2fe 100644
    > --- a/arch/s390/kvm/pv.c
    > +++ b/arch/s390/kvm/pv.c
    > @@ -196,7 +196,7 @@ int kvm_s390_pv_init_vm(struct kvm *kvm, u16 *rc, u16 *rrc)
    > uvcb.conf_base_stor_origin = (u64)kvm->arch.pv.stor_base;
    > uvcb.conf_virt_stor_origin = (u64)kvm->arch.pv.stor_var;
    >
    > - cc = uv_call(0, (u64)&uvcb);
    > + cc = uv_call_sched(0, (u64)&uvcb);
    > *rc = uvcb.header.rc;
    > *rrc = uvcb.header.rrc;
    > KVM_UV_EVENT(kvm, 3, "PROTVIRT CREATE VM: handle %llx len %llx rc %x rrc %x",
    >

    \
     
     \ /
      Last update: 2021-07-29 11:59    [W:2.563 / U:0.308 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site