| Message ID | 1523744804-8220-1-git-send-email-karahmed@amazon.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On Sun, 2018-04-15 at 00:26 +0200, KarimAllah Ahmed wrote: > Switch 'requests' to be explicitly 64-bit and update BUILD_BUG_ON check to > use the size of "requests" instead of the hard-coded '32'. > > That gives us a bit more room again for arch-specific requests as we > already ran out of space for x86 due to the hard-coded check. > > Cc: Paolo Bonzini <pbonzini@redhat.com> > Cc: Radim Krčmář <rkrcmar@redhat.com> > Cc: kvm@vger.kernel.org > Cc: linux-kernel@vger.kernel.org > Signed-off-by: KarimAllah Ahmed <karahmed@amazon.de> > --- > include/linux/kvm_host.h | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > index 6930c63..fe4f46b 100644 > --- a/include/linux/kvm_host.h > +++ b/include/linux/kvm_host.h > @@ -129,7 +129,7 @@ static inline bool is_error_page(struct page *page) > #define KVM_REQUEST_ARCH_BASE 8 > > #define KVM_ARCH_REQ_FLAGS(nr, flags) ({ \ > - BUILD_BUG_ON((unsigned)(nr) >= 32 - KVM_REQUEST_ARCH_BASE); \ > + BUILD_BUG_ON((unsigned)(nr) >= (sizeof(((struct kvm_vcpu *)0)->requests) * 8) - KVM_REQUEST_ARCH_BASE); \ While looking at a completely unrelated code I realize that there is FIELD_SIZEOF that is doing exactly what I did. Will use it in v2. > (unsigned)(((nr) + KVM_REQUEST_ARCH_BASE) | (flags)); \ > }) > #define KVM_ARCH_REQ(nr) KVM_ARCH_REQ_FLAGS(nr, 0) > @@ -223,7 +223,7 @@ struct kvm_vcpu { > int vcpu_id; > int srcu_idx; > int mode; > - unsigned long requests; > + u64 requests; > unsigned long guest_debug; > > int pre_pcpu; > @@ -1122,7 +1122,7 @@ static inline void kvm_make_request(int req, struct kvm_vcpu *vcpu) > * caller. Paired with the smp_mb__after_atomic in kvm_check_request. > */ > smp_wmb(); > - set_bit(req & KVM_REQUEST_MASK, &vcpu->requests); > + set_bit(req & KVM_REQUEST_MASK, (void *)&vcpu->requests); > } > > static inline bool kvm_request_pending(struct kvm_vcpu *vcpu) > @@ -1132,12 +1132,12 @@ static inline bool kvm_request_pending(struct kvm_vcpu *vcpu) > > static inline bool kvm_test_request(int req, struct kvm_vcpu *vcpu) > { > - return test_bit(req & KVM_REQUEST_MASK, &vcpu->requests); > + return test_bit(req & KVM_REQUEST_MASK, (void *)&vcpu->requests); > } > > static inline void kvm_clear_request(int req, struct kvm_vcpu *vcpu) > { > - clear_bit(req & KVM_REQUEST_MASK, &vcpu->requests); > + clear_bit(req & KVM_REQUEST_MASK, (void *)&vcpu->requests); > } > > static inline bool kvm_check_request(int req, struct kvm_vcpu *vcpu) Amazon Development Center Germany GmbH Berlin - Dresden - Aachen main office: Krausenstr. 38, 10117 Berlin Geschaeftsfuehrer: Dr. Ralf Herbrich, Christian Schlaeger Ust-ID: DE289237879 Eingetragen am Amtsgericht Charlottenburg HRB 149173 B
On Sun, Apr 15, 2018 at 6:12 AM, Raslan, KarimAllah <karahmed@amazon.de> wrote: > On Sun, 2018-04-15 at 00:26 +0200, KarimAllah Ahmed wrote: >> Switch 'requests' to be explicitly 64-bit and update BUILD_BUG_ON check to >> use the size of "requests" instead of the hard-coded '32'. >> >> That gives us a bit more room again for arch-specific requests as we >> already ran out of space for x86 due to the hard-coded check. >> >> Cc: Paolo Bonzini <pbonzini@redhat.com> >> Cc: Radim Krčmář <rkrcmar@redhat.com> >> Cc: kvm@vger.kernel.org >> Cc: linux-kernel@vger.kernel.org >> Signed-off-by: KarimAllah Ahmed <karahmed@amazon.de> I like it! Reviewed-by: Jim Mattson <jmattson@google.com>
On 15/04/2018 00:26, KarimAllah Ahmed wrote: > Switch 'requests' to be explicitly 64-bit and update BUILD_BUG_ON check to > use the size of "requests" instead of the hard-coded '32'. > > That gives us a bit more room again for arch-specific requests as we > already ran out of space for x86 due to the hard-coded check. > > Cc: Paolo Bonzini <pbonzini@redhat.com> > Cc: Radim Krčmář <rkrcmar@redhat.com> > Cc: kvm@vger.kernel.org > Cc: linux-kernel@vger.kernel.org > Signed-off-by: KarimAllah Ahmed <karahmed@amazon.de> I'm afraid architectures like ARM 32 need this to be conditional (using Kconfig). Thanks, Paolo > --- > include/linux/kvm_host.h | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > index 6930c63..fe4f46b 100644 > --- a/include/linux/kvm_host.h > +++ b/include/linux/kvm_host.h > @@ -129,7 +129,7 @@ static inline bool is_error_page(struct page *page) > #define KVM_REQUEST_ARCH_BASE 8 > > #define KVM_ARCH_REQ_FLAGS(nr, flags) ({ \ > - BUILD_BUG_ON((unsigned)(nr) >= 32 - KVM_REQUEST_ARCH_BASE); \ > + BUILD_BUG_ON((unsigned)(nr) >= (sizeof(((struct kvm_vcpu *)0)->requests) * 8) - KVM_REQUEST_ARCH_BASE); \ > (unsigned)(((nr) + KVM_REQUEST_ARCH_BASE) | (flags)); \ > }) > #define KVM_ARCH_REQ(nr) KVM_ARCH_REQ_FLAGS(nr, 0) > @@ -223,7 +223,7 @@ struct kvm_vcpu { > int vcpu_id; > int srcu_idx; > int mode; > - unsigned long requests; > + u64 requests; > unsigned long guest_debug; > > int pre_pcpu; > @@ -1122,7 +1122,7 @@ static inline void kvm_make_request(int req, struct kvm_vcpu *vcpu) > * caller. Paired with the smp_mb__after_atomic in kvm_check_request. > */ > smp_wmb(); > - set_bit(req & KVM_REQUEST_MASK, &vcpu->requests); > + set_bit(req & KVM_REQUEST_MASK, (void *)&vcpu->requests); > } > > static inline bool kvm_request_pending(struct kvm_vcpu *vcpu) > @@ -1132,12 +1132,12 @@ static inline bool kvm_request_pending(struct kvm_vcpu *vcpu) > > static inline bool kvm_test_request(int req, struct kvm_vcpu *vcpu) > { > - return test_bit(req & KVM_REQUEST_MASK, &vcpu->requests); > + return test_bit(req & KVM_REQUEST_MASK, (void *)&vcpu->requests); > } > > static inline void kvm_clear_request(int req, struct kvm_vcpu *vcpu) > { > - clear_bit(req & KVM_REQUEST_MASK, &vcpu->requests); > + clear_bit(req & KVM_REQUEST_MASK, (void *)&vcpu->requests); > } > > static inline bool kvm_check_request(int req, struct kvm_vcpu *vcpu) >
On Mon, 2018-04-16 at 18:28 +0200, Paolo Bonzini wrote: > On 15/04/2018 00:26, KarimAllah Ahmed wrote: > > > > Switch 'requests' to be explicitly 64-bit and update BUILD_BUG_ON check to > > use the size of "requests" instead of the hard-coded '32'. > > > > That gives us a bit more room again for arch-specific requests as we > > already ran out of space for x86 due to the hard-coded check. > > > > Cc: Paolo Bonzini <pbonzini@redhat.com> > > Cc: Radim Krčmář <rkrcmar@redhat.com> > > Cc: kvm@vger.kernel.org > > Cc: linux-kernel@vger.kernel.org > > Signed-off-by: KarimAllah Ahmed <karahmed@amazon.de> > > I'm afraid architectures like ARM 32 need this to be conditional (using > Kconfig). Why would using a 64-bit 'requests' be a problem for ARM32? Are you concerned about performance here or is there some symantic problem? > > Thanks, > > Paolo > > > > > --- > > include/linux/kvm_host.h | 10 +++++----- > > 1 file changed, 5 insertions(+), 5 deletions(-) > > > > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > > index 6930c63..fe4f46b 100644 > > --- a/include/linux/kvm_host.h > > +++ b/include/linux/kvm_host.h > > @@ -129,7 +129,7 @@ static inline bool is_error_page(struct page *page) > > #define KVM_REQUEST_ARCH_BASE 8 > > > > #define KVM_ARCH_REQ_FLAGS(nr, flags) ({ \ > > - BUILD_BUG_ON((unsigned)(nr) >= 32 - KVM_REQUEST_ARCH_BASE); \ > > + BUILD_BUG_ON((unsigned)(nr) >= (sizeof(((struct kvm_vcpu *)0)->requests) * 8) - KVM_REQUEST_ARCH_BASE); \ > > (unsigned)(((nr) + KVM_REQUEST_ARCH_BASE) | (flags)); \ > > }) > > #define KVM_ARCH_REQ(nr) KVM_ARCH_REQ_FLAGS(nr, 0) > > @@ -223,7 +223,7 @@ struct kvm_vcpu { > > int vcpu_id; > > int srcu_idx; > > int mode; > > - unsigned long requests; > > + u64 requests; > > unsigned long guest_debug; > > > > int pre_pcpu; > > @@ -1122,7 +1122,7 @@ static inline void kvm_make_request(int req, struct kvm_vcpu *vcpu) > > * caller. Paired with the smp_mb__after_atomic in kvm_check_request. > > */ > > smp_wmb(); > > - set_bit(req & KVM_REQUEST_MASK, &vcpu->requests); > > + set_bit(req & KVM_REQUEST_MASK, (void *)&vcpu->requests); > > } > > > > static inline bool kvm_request_pending(struct kvm_vcpu *vcpu) > > @@ -1132,12 +1132,12 @@ static inline bool kvm_request_pending(struct kvm_vcpu *vcpu) > > > > static inline bool kvm_test_request(int req, struct kvm_vcpu *vcpu) > > { > > - return test_bit(req & KVM_REQUEST_MASK, &vcpu->requests); > > + return test_bit(req & KVM_REQUEST_MASK, (void *)&vcpu->requests); > > } > > > > static inline void kvm_clear_request(int req, struct kvm_vcpu *vcpu) > > { > > - clear_bit(req & KVM_REQUEST_MASK, &vcpu->requests); > > + clear_bit(req & KVM_REQUEST_MASK, (void *)&vcpu->requests); > > } > > > > static inline bool kvm_check_request(int req, struct kvm_vcpu *vcpu) > > > > Amazon Development Center Germany GmbH Berlin - Dresden - Aachen main office: Krausenstr. 38, 10117 Berlin Geschaeftsfuehrer: Dr. Ralf Herbrich, Christian Schlaeger Ust-ID: DE289237879 Eingetragen am Amtsgericht Charlottenburg HRB 149173 B
On 22/05/2018 17:42, Raslan, KarimAllah wrote: > On Mon, 2018-04-16 at 18:28 +0200, Paolo Bonzini wrote: >> On 15/04/2018 00:26, KarimAllah Ahmed wrote: >>> >>> Switch 'requests' to be explicitly 64-bit and update BUILD_BUG_ON check to >>> use the size of "requests" instead of the hard-coded '32'. >>> >>> That gives us a bit more room again for arch-specific requests as we >>> already ran out of space for x86 due to the hard-coded check. >>> >>> Cc: Paolo Bonzini <pbonzini@redhat.com> >>> Cc: Radim Krčmář <rkrcmar@redhat.com> >>> Cc: kvm@vger.kernel.org >>> Cc: linux-kernel@vger.kernel.org >>> Signed-off-by: KarimAllah Ahmed <karahmed@amazon.de> >> >> I'm afraid architectures like ARM 32 need this to be conditional (using >> Kconfig). > > Why would using a 64-bit 'requests' be a problem for ARM32? Are you > concerned about performance here or is there some symantic problem? They don't support atomics on double-word data. Paolo
On Tue, 2018-05-22 at 17:47 +0200, Paolo Bonzini wrote: > On 22/05/2018 17:42, Raslan, KarimAllah wrote: > > > > On Mon, 2018-04-16 at 18:28 +0200, Paolo Bonzini wrote: > > > > > > On 15/04/2018 00:26, KarimAllah Ahmed wrote: > > > > > > > > > > > > Switch 'requests' to be explicitly 64-bit and update BUILD_BUG_ON check to > > > > use the size of "requests" instead of the hard-coded '32'. > > > > > > > > That gives us a bit more room again for arch-specific requests as we > > > > already ran out of space for x86 due to the hard-coded check. > > > > > > > > Cc: Paolo Bonzini <pbonzini@redhat.com> > > > > Cc: Radim Krčmář <rkrcmar@redhat.com> > > > > Cc: kvm@vger.kernel.org > > > > Cc: linux-kernel@vger.kernel.org > > > > Signed-off-by: KarimAllah Ahmed <karahmed@amazon.de> > > > > > > I'm afraid architectures like ARM 32 need this to be conditional (using > > > Kconfig). > > > > Why would using a 64-bit 'requests' be a problem for ARM32? Are you > > concerned about performance here or is there some symantic problem? > > They don't support atomics on double-word data. But they support atomics on single words. Of which there are two. We don't need atomic updates of the whole 64-bit quantity (a là cmpxchg). Do we strictly need this to be atomic accross the 64-bit? Looking at the use cases for "requests": kvm_clear_request kvm_test_request kvm_request_pending kvm_check_request ... and all of them would still work if the atomicity is only at the word level, right? > > Paolo > Amazon Development Center Germany GmbH Berlin - Dresden - Aachen main office: Krausenstr. 38, 10117 Berlin Geschaeftsfuehrer: Dr. Ralf Herbrich, Christian Schlaeger Ust-ID: DE289237879 Eingetragen am Amtsgericht Charlottenburg HRB 149173 B
On 05/07/2018 14:22, Raslan, KarimAllah wrote: >> They don't support atomics on double-word data. > But they support atomics on single words. Of which there are two. > We don't need atomic updates of the whole 64-bit quantity (a là > cmpxchg). Do we strictly need this to be atomic accross the 64-bit? > > Looking at the use cases for "requests": > > kvm_clear_request > kvm_test_request > kvm_request_pending > kvm_check_request > > ... and all of them would still work if the atomicity is only at the > word level, right? > Good point! Then yes, requests can be made 64 bit wide. Paolo
On Sun, Apr 15, 2018 at 12:26:44AM +0200, KarimAllah Ahmed wrote: > Switch 'requests' to be explicitly 64-bit and update BUILD_BUG_ON check to > use the size of "requests" instead of the hard-coded '32'. > > That gives us a bit more room again for arch-specific requests as we > already ran out of space for x86 due to the hard-coded check. > > Cc: Paolo Bonzini <pbonzini@redhat.com> > Cc: Radim Krčmář <rkrcmar@redhat.com> > Cc: kvm@vger.kernel.org > Cc: linux-kernel@vger.kernel.org > Signed-off-by: KarimAllah Ahmed <karahmed@amazon.de> > --- > include/linux/kvm_host.h | 10 +++++----- > 1 file changed, 5 insertions(+), 5 deletions(-) > > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > index 6930c63..fe4f46b 100644 > --- a/include/linux/kvm_host.h > +++ b/include/linux/kvm_host.h > @@ -129,7 +129,7 @@ static inline bool is_error_page(struct page *page) > #define KVM_REQUEST_ARCH_BASE 8 > > #define KVM_ARCH_REQ_FLAGS(nr, flags) ({ \ > - BUILD_BUG_ON((unsigned)(nr) >= 32 - KVM_REQUEST_ARCH_BASE); \ > + BUILD_BUG_ON((unsigned)(nr) >= (sizeof(((struct kvm_vcpu *)0)->requests) * 8) - KVM_REQUEST_ARCH_BASE); \ > (unsigned)(((nr) + KVM_REQUEST_ARCH_BASE) | (flags)); \ > }) > #define KVM_ARCH_REQ(nr) KVM_ARCH_REQ_FLAGS(nr, 0) > @@ -223,7 +223,7 @@ struct kvm_vcpu { > int vcpu_id; > int srcu_idx; > int mode; > - unsigned long requests; > + u64 requests; The usual thing to do for bitmaps is something like: #define KVM_REQUEST_NR (KVM_REQUEST_ARCH_BASE + KVM_REQUEST_ARCH_NR) unsigned long requests[BITS_TO_LONGS(NR_KVM_REQUESTS)]; > unsigned long guest_debug; > > int pre_pcpu; > @@ -1122,7 +1122,7 @@ static inline void kvm_make_request(int req, struct kvm_vcpu *vcpu) > * caller. Paired with the smp_mb__after_atomic in kvm_check_request. > */ > smp_wmb(); > - set_bit(req & KVM_REQUEST_MASK, &vcpu->requests); > + set_bit(req & KVM_REQUEST_MASK, (void *)&vcpu->requests); ... which wouldn't require a void cast to make the bit API functions happy (as these expect a pointer to the first unsigned long in the bitmap). Thanks, Mark.
On Thu, 2018-07-05 at 14:51 +0100, Mark Rutland wrote: > On Sun, Apr 15, 2018 at 12:26:44AM +0200, KarimAllah Ahmed wrote: > > > > Switch 'requests' to be explicitly 64-bit and update BUILD_BUG_ON check to > > use the size of "requests" instead of the hard-coded '32'. > > > > That gives us a bit more room again for arch-specific requests as we > > already ran out of space for x86 due to the hard-coded check. > > > > Cc: Paolo Bonzini <pbonzini@redhat.com> > > Cc: Radim Krčmář <rkrcmar@redhat.com> > > Cc: kvm@vger.kernel.org > > Cc: linux-kernel@vger.kernel.org > > Signed-off-by: KarimAllah Ahmed <karahmed@amazon.de> > > --- > > include/linux/kvm_host.h | 10 +++++----- > > 1 file changed, 5 insertions(+), 5 deletions(-) > > > > diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h > > index 6930c63..fe4f46b 100644 > > --- a/include/linux/kvm_host.h > > +++ b/include/linux/kvm_host.h > > @@ -129,7 +129,7 @@ static inline bool is_error_page(struct page *page) > > #define KVM_REQUEST_ARCH_BASE 8 > > > > #define KVM_ARCH_REQ_FLAGS(nr, flags) ({ \ > > - BUILD_BUG_ON((unsigned)(nr) >= 32 - KVM_REQUEST_ARCH_BASE); \ > > + BUILD_BUG_ON((unsigned)(nr) >= (sizeof(((struct kvm_vcpu *)0)->requests) * 8) - KVM_REQUEST_ARCH_BASE); \ > > (unsigned)(((nr) + KVM_REQUEST_ARCH_BASE) | (flags)); \ > > }) > > #define KVM_ARCH_REQ(nr) KVM_ARCH_REQ_FLAGS(nr, 0) > > @@ -223,7 +223,7 @@ struct kvm_vcpu { > > int vcpu_id; > > int srcu_idx; > > int mode; > > - unsigned long requests; > > + u64 requests; > > The usual thing to do for bitmaps is something like: > > #define KVM_REQUEST_NR (KVM_REQUEST_ARCH_BASE + KVM_REQUEST_ARCH_NR) > > unsigned long requests[BITS_TO_LONGS(NR_KVM_REQUESTS)]; > > > > > unsigned long guest_debug; > > > > int pre_pcpu; > > @@ -1122,7 +1122,7 @@ static inline void kvm_make_request(int req, struct kvm_vcpu *vcpu) > > * caller. Paired with the smp_mb__after_atomic in kvm_check_request. > > */ > > smp_wmb(); > > - set_bit(req & KVM_REQUEST_MASK, &vcpu->requests); > > + set_bit(req & KVM_REQUEST_MASK, (void *)&vcpu->requests); > > ... which wouldn't require a void cast to make the bit API functions > happy (as these expect a pointer to the first unsigned long in the > bitmap). Ah, right! Good point. Paolo, Would you prefer to switch "requests" to a bitmap and update kvm_request_pending to handle this? > > Thanks, > Mark. > Amazon Development Center Germany GmbH Berlin - Dresden - Aachen main office: Krausenstr. 38, 10117 Berlin Geschaeftsfuehrer: Dr. Ralf Herbrich, Christian Schlaeger Ust-ID: DE289237879 Eingetragen am Amtsgericht Charlottenburg HRB 149173 B
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 6930c63..fe4f46b 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -129,7 +129,7 @@ static inline bool is_error_page(struct page *page) #define KVM_REQUEST_ARCH_BASE 8 #define KVM_ARCH_REQ_FLAGS(nr, flags) ({ \ - BUILD_BUG_ON((unsigned)(nr) >= 32 - KVM_REQUEST_ARCH_BASE); \ + BUILD_BUG_ON((unsigned)(nr) >= (sizeof(((struct kvm_vcpu *)0)->requests) * 8) - KVM_REQUEST_ARCH_BASE); \ (unsigned)(((nr) + KVM_REQUEST_ARCH_BASE) | (flags)); \ }) #define KVM_ARCH_REQ(nr) KVM_ARCH_REQ_FLAGS(nr, 0) @@ -223,7 +223,7 @@ struct kvm_vcpu { int vcpu_id; int srcu_idx; int mode; - unsigned long requests; + u64 requests; unsigned long guest_debug; int pre_pcpu; @@ -1122,7 +1122,7 @@ static inline void kvm_make_request(int req, struct kvm_vcpu *vcpu) * caller. Paired with the smp_mb__after_atomic in kvm_check_request. */ smp_wmb(); - set_bit(req & KVM_REQUEST_MASK, &vcpu->requests); + set_bit(req & KVM_REQUEST_MASK, (void *)&vcpu->requests); } static inline bool kvm_request_pending(struct kvm_vcpu *vcpu) @@ -1132,12 +1132,12 @@ static inline bool kvm_request_pending(struct kvm_vcpu *vcpu) static inline bool kvm_test_request(int req, struct kvm_vcpu *vcpu) { - return test_bit(req & KVM_REQUEST_MASK, &vcpu->requests); + return test_bit(req & KVM_REQUEST_MASK, (void *)&vcpu->requests); } static inline void kvm_clear_request(int req, struct kvm_vcpu *vcpu) { - clear_bit(req & KVM_REQUEST_MASK, &vcpu->requests); + clear_bit(req & KVM_REQUEST_MASK, (void *)&vcpu->requests); } static inline bool kvm_check_request(int req, struct kvm_vcpu *vcpu)
Switch 'requests' to be explicitly 64-bit and update BUILD_BUG_ON check to use the size of "requests" instead of the hard-coded '32'. That gives us a bit more room again for arch-specific requests as we already ran out of space for x86 due to the hard-coded check. Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Radim Krčmář <rkrcmar@redhat.com> Cc: kvm@vger.kernel.org Cc: linux-kernel@vger.kernel.org Signed-off-by: KarimAllah Ahmed <karahmed@amazon.de> --- include/linux/kvm_host.h | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-)