* Re: Re: [PATCH] KVM:arm/arm64: dcache need be coherent unconditionally
@ 2018-03-10 3:48 ` peng.hao2 at zte.com.cn
0 siblings, 0 replies; 3+ messages in thread
From: peng.hao2 @ 2018-03-10 3:48 UTC (permalink / raw)
To: marc.zyngier; +Cc: cdall, linux-kernel, linux-arm-kernel, kvmarm
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>On 09/03/18 22:15, Peng Hao wrote:
>> For emulation devices just like vga, keeping coherent dcache between
>> guest and host timely is needed.
>> Now the display of vnc-viewer will not update continuously and the
>> patch can fix up.
>>
>> Signed-off-by: Peng Hao <peng.hao2@zte.com.cn>
>> ---
>> virt/kvm/arm/mmu.c | 6 ++----
>> 1 file changed, 2 insertions(+), 4 deletions(-)
>>
>> diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
>> index ec62d1c..4a28395e 100644
>> --- a/virt/kvm/arm/mmu.c
>> +++ b/virt/kvm/arm/mmu.c
>> @@ -1416,8 +1416,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>> kvm_set_pfn_dirty(pfn);
>> }
>>
>> - if (fault_status != FSC_PERM)
>> - clean_dcache_guest_page(pfn, PMD_SIZE);
>> + clean_dcache_guest_page(pfn, PMD_SIZE);
>>
>> if (exec_fault) {
>> new_pmd = kvm_s2pmd_mkexec(new_pmd);
>> @@ -1438,8 +1437,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>> mark_page_dirty(kvm, gfn);
>> }
>>
>> - if (fault_status != FSC_PERM)
>> - clean_dcache_guest_page(pfn, PAGE_SIZE);
>> + clean_dcache_guest_page(pfn, PAGE_SIZE);
>>
>> if (exec_fault) {
>> new_pte = kvm_s2pte_mkexec(new_pte);
>>
>I'm sorry, but I have to NAK this.
>You're papering over the fundamental issue that you're accessing a
>cacheable alias of a non cacheable memory. The architecture is very
>clear about why this doesn't work, and KVM implements the architecture.
I find that I just encounter the problem after the commit '15303ba5d1cd9b28d03a980456c0978c0ea3b208 " .
The commit contains "icache invalidation optimizations, improving VM startup time",it changes
from unconditionally calling coherent_cache_guest_page(including dcache handle) to conditionally calling clean_dcache_guest_page.
I trace the display of vnc abnormally and find it generate data abort in vga
address region with FSC_PERM,and it will not call clean_dcache_guest_page . So I think should recover to uncontionally calling clean_dcache_guest_page.
Thanks.
>If you want this to work, map your VGA device as cacheable, add cache
>maintenance to QEMU, or use another frame-buffer emulation that doesn't
>require such a gack.
>Thanks,
> M.
>--
>Jazz is not dead. It just smells funny...
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^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Re: [PATCH] KVM:arm/arm64: dcache need be coherent unconditionally
@ 2018-03-10 3:48 ` peng.hao2 at zte.com.cn
0 siblings, 0 replies; 3+ messages in thread
From: peng.hao2 at zte.com.cn @ 2018-03-10 3:48 UTC (permalink / raw)
To: linux-arm-kernel
>On 09/03/18 22:15, Peng Hao wrote:
>> For emulation devices just like vga, keeping coherent dcache between
>> guest and host timely is needed.
>> Now the display of vnc-viewer will not update continuously and the
>> patch can fix up.
>>
>> Signed-off-by: Peng Hao <peng.hao2@zte.com.cn>
>> ---
>> virt/kvm/arm/mmu.c | 6 ++----
>> 1 file changed, 2 insertions(+), 4 deletions(-)
>>
>> diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
>> index ec62d1c..4a28395e 100644
>> --- a/virt/kvm/arm/mmu.c
>> +++ b/virt/kvm/arm/mmu.c
>> @@ -1416,8 +1416,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>> kvm_set_pfn_dirty(pfn);
>> }
>>
>> - if (fault_status != FSC_PERM)
>> - clean_dcache_guest_page(pfn, PMD_SIZE);
>> + clean_dcache_guest_page(pfn, PMD_SIZE);
>>
>> if (exec_fault) {
>> new_pmd = kvm_s2pmd_mkexec(new_pmd);
>> @@ -1438,8 +1437,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>> mark_page_dirty(kvm, gfn);
>> }
>>
>> - if (fault_status != FSC_PERM)
>> - clean_dcache_guest_page(pfn, PAGE_SIZE);
>> + clean_dcache_guest_page(pfn, PAGE_SIZE);
>>
>> if (exec_fault) {
>> new_pte = kvm_s2pte_mkexec(new_pte);
>>
>I'm sorry, but I have to NAK this.
>You're papering over the fundamental issue that you're accessing a
>cacheable alias of a non cacheable memory. The architecture is very
>clear about why this doesn't work, and KVM implements the architecture.
I find that I just encounter the problem after the commit '15303ba5d1cd9b28d03a980456c0978c0ea3b208 " .
The commit contains "icache invalidation optimizations, improving VM startup time",it changes
from unconditionally calling coherent_cache_guest_page(including dcache handle) to conditionally calling clean_dcache_guest_page.
I trace the display of vnc abnormally and find it generate data abort in vga
address region with FSC_PERM,and it will not call clean_dcache_guest_page . So I think should recover to uncontionally calling clean_dcache_guest_page.
Thanks.
>If you want this to work, map your VGA device as cacheable, add cache
>maintenance to QEMU, or use another frame-buffer emulation that doesn't
>require such a gack.
>Thanks,
> M.
>--
>Jazz is not dead. It just smells funny...
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: Re: [PATCH] KVM:arm/arm64: dcache need be coherent unconditionally
2018-03-09 14:21 Marc Zyngier
@ 2018-03-10 3:23 ` peng.hao2
0 siblings, 0 replies; 3+ messages in thread
From: peng.hao2 @ 2018-03-10 3:23 UTC (permalink / raw)
To: marc.zyngier; +Cc: kvmarm, linux-arm-kernel, linux-kernel
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>On 09/03/18 22:15, Peng Hao wrote:
>> For emulation devices just like vga, keeping coherent dcache between
>> guest and host timely is needed.
>> Now the display of vnc-viewer will not update continuously and the
>> patch can fix up.
>>
>> Signed-off-by: Peng Hao <peng.hao2@zte.com.cn>
>> ---
>> virt/kvm/arm/mmu.c | 6 ++----
>> 1 file changed, 2 insertions(+), 4 deletions(-)
>>
>> diff --git a/virt/kvm/arm/mmu.c b/virt/kvm/arm/mmu.c
>> index ec62d1c..4a28395e 100644
>> --- a/virt/kvm/arm/mmu.c
>> +++ b/virt/kvm/arm/mmu.c
>> @@ -1416,8 +1416,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>> kvm_set_pfn_dirty(pfn);
>> }
>>
>> - if (fault_status != FSC_PERM)
>> - clean_dcache_guest_page(pfn, PMD_SIZE);
>> + clean_dcache_guest_page(pfn, PMD_SIZE);
>>
>> if (exec_fault) {
>> new_pmd = kvm_s2pmd_mkexec(new_pmd);
>> @@ -1438,8 +1437,7 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>> mark_page_dirty(kvm, gfn);
>> }
>>
>> - if (fault_status != FSC_PERM)
>> - clean_dcache_guest_page(pfn, PAGE_SIZE);
>> + clean_dcache_guest_page(pfn, PAGE_SIZE);
>>
>> if (exec_fault) {
>> new_pte = kvm_s2pte_mkexec(new_pte);
>>
>I'm sorry, but I have to NAK this.
>You're papering over the fundamental issue that you're accessing a
>cacheable alias of a non cacheable memory. The architecture is very
>clear about why this doesn't work, and KVM implements the architecture.
I find that I just encounter the problem after the commit '15303ba5d1cd9b28d03a980456c0978c0ea3b208 " .
The commit contains "icache invalidation optimizations, improving VM startup time",it changes
from unconditionally calling coherent_cache_guest_page(including dcache handle) to conditionally calling clean_dcache_guest_page.
I trace the display of vnc abnormally and find it generate data abort in vga
address region with FSC_PERM,and it will not call clean_dcache_guest_page . So I think should recover to uncontionally calling clean_dcache_guest_page.
Thanks.
>If you want this to work, map your VGA device as cacheable, add cache
>maintenance to QEMU, or use another frame-buffer emulation that doesn't
>require such a gack.
>Thanks,
> M.
>--
>Jazz is not dead. It just smells funny...
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https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
^ permalink raw reply [flat|nested] 3+ messages in thread
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2018-03-10 3:48 Re: [PATCH] KVM:arm/arm64: dcache need be coherent unconditionally peng.hao2
2018-03-10 3:48 ` peng.hao2 at zte.com.cn
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2018-03-09 14:21 Marc Zyngier
2018-03-10 3:23 ` peng.hao2
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