From: Paul Durrant <xadimgnik@gmail.com>
To: David Woodhouse <dwmw2@infradead.org>,
Sean Christopherson <seanjc@google.com>,
Paolo Bonzini <pbonzini@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
Dave Hansen <dave.hansen@linux.intel.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
kvm@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v8 08/15] KVM: pfncache: allow a cache to be activated with a fixed (userspace) HVA
Date: Wed, 22 Nov 2023 10:07:00 +0000 [thread overview]
Message-ID: <5e0e13ea-3eee-41bd-a070-e7bd9ed5d2e9@xen.org> (raw)
In-Reply-To: <ec89ab12288426761ab5bd7d05562a4e8834e5f1.camel@infradead.org>
On 21/11/2023 22:47, David Woodhouse wrote:
> On Tue, 2023-11-21 at 18:02 +0000, Paul Durrant wrote:
>>
>> -static int __kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa,
>> +static int __kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, u64 addr, bool addr_is_gpa,
>> unsigned long len)
>> {
>> struct kvm_memslots *slots = kvm_memslots(gpc->kvm);
>> - unsigned long page_offset = offset_in_page(gpa);
>> + unsigned long page_offset = offset_in_page(addr);
>> bool unmap_old = false;
>> kvm_pfn_t old_pfn;
>> bool hva_change = false;
>> @@ -244,12 +244,21 @@ static int __kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa,
>> old_pfn = gpc->pfn;
>> old_khva = (void *)PAGE_ALIGN_DOWN((uintptr_t)gpc->khva);
>>
>> - /* If the userspace HVA is invalid, refresh that first */
>> - if (gpc->gpa != gpa || gpc->generation != slots->generation ||
>> - kvm_is_error_hva(gpc->uhva)) {
>> - gfn_t gfn = gpa_to_gfn(gpa);
>> + if (!addr_is_gpa) {
>> + gpc->gpa = KVM_XEN_INVALID_GPA;
>> + gpc->uhva = PAGE_ALIGN_DOWN(gpc->uhva);
>> + addr = PAGE_ALIGN_DOWN(addr);
>> +
>> + if (gpc->uhva != addr) {
>> + gpc->uhva = addr;
>> + hva_change = true;
>> + }
>> + } else if (gpc->gpa != addr ||
>> + gpc->generation != slots->generation ||
>> + kvm_is_error_hva(gpc->uhva)) {
>> + gfn_t gfn = gpa_to_gfn(addr);
>>
>> - gpc->gpa = gpa;
>> + gpc->gpa = addr;
>> gpc->generation = slots->generation;
>> gpc->memslot = __gfn_to_memslot(slots, gfn);
>> gpc->uhva = gfn_to_hva_memslot(gpc->memslot, gfn);
>
> Hrm, now that a previous patch means we're preserving the low bits of
> gpc->uhva surely you don't *need* to mess with the gpc struct?
>
I'm not messing with it, am I?
> If gpc->gpa == KVM_XEN_INVALID_GPA (but gpc->uhva != KVM_ERR_ERR_BAD &&
> gpc->active) surely that's enough to signal that gpc->uhva is canonical
> and doesn't need to be looked up from the GPA?
>
> And I think that means the 'bool addr_is_gpa' argument can go away from
> __kvm_gpc_refresh(); you can set it up in {__,}kvm_gpc_activate*()
> instead?
Alas not... __kvm_gpc_refresh() still needs to know *something* has
changed, otherwise the khva will be stale.
Paul
next prev parent reply other threads:[~2023-11-22 10:07 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-11-21 18:02 [PATCH v8 00/15] KVM: xen: update shared_info and vcpu_info handling Paul Durrant
2023-11-21 18:02 ` [PATCH v8 01/15] KVM: pfncache: Add a map helper function Paul Durrant
2023-11-21 18:02 ` [PATCH v8 02/15] KVM: pfncache: remove unnecessary exports Paul Durrant
2023-11-21 21:49 ` David Woodhouse
2023-11-22 8:44 ` Paul Durrant
2023-11-21 18:02 ` [PATCH v8 03/15] KVM: xen: mark guest pages dirty with the pfncache lock held Paul Durrant
2023-11-21 21:49 ` David Woodhouse
2023-11-21 18:02 ` [PATCH v8 04/15] KVM: pfncache: add a mark-dirty helper Paul Durrant
2023-11-21 18:02 ` [PATCH v8 05/15] KVM: pfncache: remove KVM_GUEST_USES_PFN usage Paul Durrant
2023-11-21 22:24 ` David Woodhouse
2023-11-27 23:36 ` Sean Christopherson
2023-11-21 18:02 ` [PATCH v8 06/15] KVM: pfncache: stop open-coding offset_in_page() Paul Durrant
2023-11-21 22:26 ` David Woodhouse
2023-11-21 18:02 ` [PATCH v8 07/15] KVM: pfncache: include page offset in uhva and use it consistently Paul Durrant
2023-11-21 22:35 ` David Woodhouse
2023-11-22 9:29 ` Paul Durrant
2023-11-22 8:54 ` Xu Yilun
2023-11-22 9:12 ` David Woodhouse
2023-11-22 14:27 ` Xu Yilun
2023-11-22 15:42 ` David Woodhouse
2023-11-22 15:52 ` Paul Durrant
2023-11-21 18:02 ` [PATCH v8 08/15] KVM: pfncache: allow a cache to be activated with a fixed (userspace) HVA Paul Durrant
2023-11-21 22:47 ` David Woodhouse
2023-11-22 10:07 ` Paul Durrant [this message]
2023-11-21 18:02 ` [PATCH v8 09/15] KVM: xen: allow shared_info to be mapped by fixed HVA Paul Durrant
2023-11-21 18:02 ` [PATCH v8 10/15] KVM: xen: allow vcpu_info " Paul Durrant
2023-11-21 18:02 ` [PATCH v8 11/15] KVM: selftests / xen: map shared_info using HVA rather than GFN Paul Durrant
2023-11-21 18:02 ` [PATCH v8 12/15] KVM: selftests / xen: re-map vcpu_info using HVA rather than GPA Paul Durrant
2023-11-21 18:02 ` [PATCH v8 13/15] KVM: xen: advertize the KVM_XEN_HVM_CONFIG_SHARED_INFO_HVA capability Paul Durrant
2023-11-21 18:02 ` [PATCH v8 14/15] KVM: xen: split up kvm_xen_set_evtchn_fast() Paul Durrant
2023-11-21 22:49 ` David Woodhouse
2023-11-21 18:02 ` [PATCH v8 15/15] KVM: xen: allow vcpu_info content to be 'safely' copied Paul Durrant
2023-11-21 22:53 ` David Woodhouse
2023-11-22 10:39 ` David Woodhouse
2023-11-22 10:55 ` Paul Durrant
2023-11-22 11:25 ` David Woodhouse
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