Re: [PATCH v2 08/11] powerpc: Mark writes registering ipi to host cpu through kvm and polling
> On 15 May 2023, at 3:53 pm, Nicholas Piggin wrote:
>
> On Wed May 10, 2023 at 1:31 PM AEST, Rohan McLure wrote:
>> Mark writes to hypervisor ipi state so that KCSAN recognises these
>> asynchronous issue of kvmppc_{set,clear}_host_ipi to be intended, with
>> atomic writes. Mark asynchronous polls to this variable in
>> kvm_ppc_read_one_intr().
>>
>> Signed-off-by: Rohan McLure
>
> What's the go with accesses in asm? Does it just assume you know
> what you're doing?
Exactly, KCSAN only emits instrumentation calls to around load/store
instructions that the compiler itself generated. So by default, asm
accesses are not instrumented.
Thanks
>
> Reviewed-by: Nicholas Piggin
>
>> ---
>> v2: Add read-side annotations to both polling locations in
>> kvm_ppc_read_one_intr().
>> ---
>> arch/powerpc/include/asm/kvm_ppc.h | 4 ++--
>> arch/powerpc/kvm/book3s_hv_builtin.c | 4 ++--
>> 2 files changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/arch/powerpc/include/asm/kvm_ppc.h
>> b/arch/powerpc/include/asm/kvm_ppc.h
>> index bc57d058ad5b..d701df006c08 100644
>> --- a/arch/powerpc/include/asm/kvm_ppc.h
>> +++ b/arch/powerpc/include/asm/kvm_ppc.h
>> @@ -548,12 +548,12 @@ static inline void kvmppc_set_host_ipi(int cpu)
>> * pairs with the barrier in kvmppc_clear_host_ipi()
>> */
>> smp_mb();
>> - paca_ptrs[cpu]->kvm_hstate.host_ipi = 1;
>> + WRITE_ONCE(paca_ptrs[cpu]->kvm_hstate.host_ipi, 1);
>> }
>>
>> static inline void kvmppc_clear_host_ipi(int cpu)
>> {
>> - paca_ptrs[cpu]->kvm_hstate.host_ipi = 0;
>> + WRITE_ONCE(paca_ptrs[cpu]->kvm_hstate.host_ipi, 0);
>> /*
>> * order clearing of host_ipi flag vs. processing of IPI messages
>> *
>> diff --git a/arch/powerpc/kvm/book3s_hv_builtin.c
>> b/arch/powerpc/kvm/book3s_hv_builtin.c
>> index da85f046377a..0f5b021fa559 100644
>> --- a/arch/powerpc/kvm/book3s_hv_builtin.c
>> +++ b/arch/powerpc/kvm/book3s_hv_builtin.c
>> @@ -406,7 +406,7 @@ static long kvmppc_read_one_intr(bool *again)
>> return 1;
>>
>> /* see if a host IPI is pending */
>> - host_ipi = local_paca->kvm_hstate.host_ipi;
>> + host_ipi = READ_ONCE(local_paca->kvm_hstate.host_ipi);
>> if (host_ipi)
>> return 1;
>>
>> @@ -466,7 +466,7 @@ static long kvmppc_read_one_intr(bool *again)
>> * meantime. If it's clear, we bounce the interrupt to the
>> * guest
>> */
>> - host_ipi = local_paca->kvm_hstate.host_ipi;
>> + host_ipi = READ_ONCE(local_paca->kvm_hstate.host_ipi);
>> if (unlikely(host_ipi != 0)) {
>> /* We raced with the host,
>> * we need to resend that IPI, bummer
>> --
>> 2.37.2
>
Re: [PATCH v2 08/11] powerpc: Mark writes registering ipi to host cpu through kvm and polling
On Wed May 10, 2023 at 1:31 PM AEST, Rohan McLure wrote:
> Mark writes to hypervisor ipi state so that KCSAN recognises these
> asynchronous issue of kvmppc_{set,clear}_host_ipi to be intended, with
> atomic writes. Mark asynchronous polls to this variable in
> kvm_ppc_read_one_intr().
>
> Signed-off-by: Rohan McLure
What's the go with accesses in asm? Does it just assume you know
what you're doing?
Reviewed-by: Nicholas Piggin
> ---
> v2: Add read-side annotations to both polling locations in
> kvm_ppc_read_one_intr().
> ---
> arch/powerpc/include/asm/kvm_ppc.h | 4 ++--
> arch/powerpc/kvm/book3s_hv_builtin.c | 4 ++--
> 2 files changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/kvm_ppc.h
> b/arch/powerpc/include/asm/kvm_ppc.h
> index bc57d058ad5b..d701df006c08 100644
> --- a/arch/powerpc/include/asm/kvm_ppc.h
> +++ b/arch/powerpc/include/asm/kvm_ppc.h
> @@ -548,12 +548,12 @@ static inline void kvmppc_set_host_ipi(int cpu)
>* pairs with the barrier in kvmppc_clear_host_ipi()
>*/
> smp_mb();
> - paca_ptrs[cpu]->kvm_hstate.host_ipi = 1;
> + WRITE_ONCE(paca_ptrs[cpu]->kvm_hstate.host_ipi, 1);
> }
>
> static inline void kvmppc_clear_host_ipi(int cpu)
> {
> - paca_ptrs[cpu]->kvm_hstate.host_ipi = 0;
> + WRITE_ONCE(paca_ptrs[cpu]->kvm_hstate.host_ipi, 0);
> /*
>* order clearing of host_ipi flag vs. processing of IPI messages
>*
> diff --git a/arch/powerpc/kvm/book3s_hv_builtin.c
> b/arch/powerpc/kvm/book3s_hv_builtin.c
> index da85f046377a..0f5b021fa559 100644
> --- a/arch/powerpc/kvm/book3s_hv_builtin.c
> +++ b/arch/powerpc/kvm/book3s_hv_builtin.c
> @@ -406,7 +406,7 @@ static long kvmppc_read_one_intr(bool *again)
> return 1;
>
> /* see if a host IPI is pending */
> - host_ipi = local_paca->kvm_hstate.host_ipi;
> + host_ipi = READ_ONCE(local_paca->kvm_hstate.host_ipi);
> if (host_ipi)
> return 1;
>
> @@ -466,7 +466,7 @@ static long kvmppc_read_one_intr(bool *again)
>* meantime. If it's clear, we bounce the interrupt to the
>* guest
>*/
> - host_ipi = local_paca->kvm_hstate.host_ipi;
> + host_ipi = READ_ONCE(local_paca->kvm_hstate.host_ipi);
> if (unlikely(host_ipi != 0)) {
> /* We raced with the host,
>* we need to resend that IPI, bummer
> --
> 2.37.2
[PATCH v2 08/11] powerpc: Mark writes registering ipi to host cpu through kvm and polling
Mark writes to hypervisor ipi state so that KCSAN recognises these
asynchronous issue of kvmppc_{set,clear}_host_ipi to be intended, with
atomic writes. Mark asynchronous polls to this variable in
kvm_ppc_read_one_intr().
Signed-off-by: Rohan McLure
---
v2: Add read-side annotations to both polling locations in
kvm_ppc_read_one_intr().
---
arch/powerpc/include/asm/kvm_ppc.h | 4 ++--
arch/powerpc/kvm/book3s_hv_builtin.c | 4 ++--
2 files changed, 4 insertions(+), 4 deletions(-)
diff --git a/arch/powerpc/include/asm/kvm_ppc.h
b/arch/powerpc/include/asm/kvm_ppc.h
index bc57d058ad5b..d701df006c08 100644
--- a/arch/powerpc/include/asm/kvm_ppc.h
+++ b/arch/powerpc/include/asm/kvm_ppc.h
@@ -548,12 +548,12 @@ static inline void kvmppc_set_host_ipi(int cpu)
* pairs with the barrier in kvmppc_clear_host_ipi()
*/
smp_mb();
- paca_ptrs[cpu]->kvm_hstate.host_ipi = 1;
+ WRITE_ONCE(paca_ptrs[cpu]->kvm_hstate.host_ipi, 1);
}
static inline void kvmppc_clear_host_ipi(int cpu)
{
- paca_ptrs[cpu]->kvm_hstate.host_ipi = 0;
+ WRITE_ONCE(paca_ptrs[cpu]->kvm_hstate.host_ipi, 0);
/*
* order clearing of host_ipi flag vs. processing of IPI messages
*
diff --git a/arch/powerpc/kvm/book3s_hv_builtin.c
b/arch/powerpc/kvm/book3s_hv_builtin.c
index da85f046377a..0f5b021fa559 100644
--- a/arch/powerpc/kvm/book3s_hv_builtin.c
+++ b/arch/powerpc/kvm/book3s_hv_builtin.c
@@ -406,7 +406,7 @@ static long kvmppc_read_one_intr(bool *again)
return 1;
/* see if a host IPI is pending */
- host_ipi = local_paca->kvm_hstate.host_ipi;
+ host_ipi = READ_ONCE(local_paca->kvm_hstate.host_ipi);
if (host_ipi)
return 1;
@@ -466,7 +466,7 @@ static long kvmppc_read_one_intr(bool *again)
* meantime. If it's clear, we bounce the interrupt to the
* guest
*/
- host_ipi = local_paca->kvm_hstate.host_ipi;
+ host_ipi = READ_ONCE(local_paca->kvm_hstate.host_ipi);
if (unlikely(host_ipi != 0)) {
/* We raced with the host,
* we need to resend that IPI, bummer
--
2.37.2
