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Re: [PATCH V15 11/11] arm/arm64: KVM: add guest SEA support

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  Re: [PATCH V15 11/11] arm/arm64: KVM: add guest SEA support Borislav Petkov <bp@alien8.de> - 2017-05-08 19:50 +0200
    Re: [PATCH V15 11/11] arm/arm64: KVM: add guest SEA support "Baicar, Tyler" <tbaicar@codeaurora.org> - 2017-05-08 22:00 +0200
      Re: [PATCH V15 11/11] arm/arm64: KVM: add guest SEA support Borislav Petkov <bp@alien8.de> - 2017-05-08 22:30 +0200

#1637619 — Re: [PATCH V15 11/11] arm/arm64: KVM: add guest SEA support

On Tue, Apr 18, 2017 at 05:05:23PM -0600, Tyler Baicar wrote:
> Currently external aborts are unsupported by the guest abort
> handling. Add handling for SEAs so that the host kernel reports
> SEAs which occur in the guest kernel.
> 
> When an SEA occurs in the guest kernel, the guest exits and is
> routed to kvm_handle_guest_abort(). Prior to this patch, a print
> message of an unsupported FSC would be printed and nothing else
> would happen. With this patch, the code gets routed to the APEI
> handling of SEAs in the host kernel to report the SEA information.
> 
> Signed-off-by: Tyler Baicar <tbaicar@codeaurora.org>
> Acked-by: Catalin Marinas <catalin.marinas@arm.com>
> Acked-by: Marc Zyngier <marc.zyngier@arm.com>
> Acked-by: Christoffer Dall <cdall@linaro.org>

...

> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
> index 582a972..fd11855 100644
> --- a/arch/arm/kvm/mmu.c
> +++ b/arch/arm/kvm/mmu.c
> @@ -29,6 +29,7 @@
>  #include <asm/kvm_asm.h>
>  #include <asm/kvm_emulate.h>
>  #include <asm/virt.h>
> +#include <asm/system_misc.h>
>  
>  #include "trace.h"
>  
> @@ -1418,6 +1419,24 @@ static void handle_access_fault(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa)
>  		kvm_set_pfn_accessed(pfn);
>  }
>  
> +static bool is_abort_sea(unsigned long fault_status) {

ERROR: open brace '{' following function declarations go on the next line
#107: FILE: arch/arm/kvm/mmu.c:1422:
+static bool is_abort_sea(unsigned long fault_status) {

...

> @@ -611,6 +612,24 @@ static int do_sea(unsigned long addr, unsigned int esr, struct pt_regs *regs)
>  };
>  
>  /*
> + * Handle Synchronous External Aborts that occur in a guest kernel.
> + *
> + * The return value will be zero if the SEA was successfully handled
> + * and non-zero if there was an error processing the error or there was
> + * no error to process.
> + */
> +int handle_guest_sea(phys_addr_t addr, unsigned int esr)
> +{
> +	int ret = -ENOENT;
> +
> +	if (IS_ENABLED(CONFIG_ACPI_APEI_SEA)) {
> +		ret = ghes_notify_sea();
> +	}

WARNING: braces {} are not necessary for single statement blocks
#239: FILE: arch/arm64/mm/fault.c:625:
+       if (IS_ENABLED(CONFIG_ACPI_APEI_SEA)) {
+               ret = ghes_notify_sea();
+       }


> +
> +	return ret;
> +}
> +
> +/*
>   * Dispatch a data abort to the relevant handler.
>   */
>  asmlinkage void __exception do_mem_abort(unsigned long addr, unsigned int esr,
> diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
> index 612deb3..d286248 100644
> --- a/drivers/acpi/apei/ghes.c
> +++ b/drivers/acpi/apei/ghes.c
> @@ -812,17 +812,18 @@ static int ghes_notify_sci(struct notifier_block *this,
>  #ifdef CONFIG_ACPI_APEI_SEA
>  static LIST_HEAD(ghes_sea);
>  
> -void ghes_notify_sea(void)
> +int ghes_notify_sea(void)
>  {
>  	struct ghes *ghes;
> +	int ret = -ENOENT;
>  
> -	/*
> -	 * synchronize_rcu() will wait for nmi_exit(), so no need to
> -	 * rcu_read_lock().
> -	 */
> +	rcu_read_lock();
>  	list_for_each_entry_rcu(ghes, &ghes_sea, list) {
> -		ghes_proc(ghes);
> +		if(!ghes_proc(ghes))
> +			ret = 0;

What is the idea here: the first time ghes_proc() returns 0, ret is set
to 0 and all errors after it will be practically ignored. Looks like it
needs more love.

Also:

ERROR: space required before the open parenthesis '('
#271: FILE: drivers/acpi/apei/ghes.c:822:
+               if(!ghes_proc(ghes))

Please integrate scripts/checkpatch.pl in your patch creation workflow.
Some of the warnings/errors *actually* make sense.

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.

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#1637682

On 5/8/2017 11:40 AM, Borislav Petkov wrote:
> On Tue, Apr 18, 2017 at 05:05:23PM -0600, Tyler Baicar wrote:
>> Currently external aborts are unsupported by the guest abort
>> handling. Add handling for SEAs so that the host kernel reports
>> SEAs which occur in the guest kernel.
>>
>> When an SEA occurs in the guest kernel, the guest exits and is
>> routed to kvm_handle_guest_abort(). Prior to this patch, a print
>> message of an unsupported FSC would be printed and nothing else
>> would happen. With this patch, the code gets routed to the APEI
>> handling of SEAs in the host kernel to report the SEA information.
>>
>> Signed-off-by: Tyler Baicar <tbaicar@codeaurora.org>
>> Acked-by: Catalin Marinas <catalin.marinas@arm.com>
>> Acked-by: Marc Zyngier <marc.zyngier@arm.com>
>> Acked-by: Christoffer Dall <cdall@linaro.org>
...
>> +
>> +	return ret;
>> +}
>> +
>> +/*
>>    * Dispatch a data abort to the relevant handler.
>>    */
>>   asmlinkage void __exception do_mem_abort(unsigned long addr, unsigned int esr,
>> diff --git a/drivers/acpi/apei/ghes.c b/drivers/acpi/apei/ghes.c
>> index 612deb3..d286248 100644
>> --- a/drivers/acpi/apei/ghes.c
>> +++ b/drivers/acpi/apei/ghes.c
>> @@ -812,17 +812,18 @@ static int ghes_notify_sci(struct notifier_block *this,
>>   #ifdef CONFIG_ACPI_APEI_SEA
>>   static LIST_HEAD(ghes_sea);
>>   
>> -void ghes_notify_sea(void)
>> +int ghes_notify_sea(void)
>>   {
>>   	struct ghes *ghes;
>> +	int ret = -ENOENT;
>>   
>> -	/*
>> -	 * synchronize_rcu() will wait for nmi_exit(), so no need to
>> -	 * rcu_read_lock().
>> -	 */
>> +	rcu_read_lock();
>>   	list_for_each_entry_rcu(ghes, &ghes_sea, list) {
>> -		ghes_proc(ghes);
>> +		if(!ghes_proc(ghes))
>> +			ret = 0;
> What is the idea here: the first time ghes_proc() returns 0, ret is set
> to 0 and all errors after it will be practically ignored. Looks like it
> needs more love.
This was discussed in the v12 and v13 patch series. There is existing 
code in kvm_handle_guest_abort
for injecting an abort back into the guest. We only want to do that if 
it was an abort that was not
handled by the firmware first handling. So here we verify that at least 
one of the SEA error sources
successfully reported an error record sent from the firmware. If there 
were no errors reported by
firmware, then we want to continue with the current implementation that 
will inject the virtual
abort. (kvm_inject_vabt)

Thanks,
Tyler

-- 
Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc.
Qualcomm Technologies, Inc. is a member of the Code Aurora Forum,
a Linux Foundation Collaborative Project.

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#1637697

On Mon, May 08, 2017 at 01:54:44PM -0600, Baicar, Tyler wrote:
> This was discussed in the v12 and v13 patch series. There is existing
> code in kvm_handle_guest_abort for injecting an abort back into the
> guest. We only want to do that if it was an abort that was not handled
> by the firmware first handling. So here we verify that at least one of
> the SEA error sources successfully reported an error record sent from
> the firmware. If there were no errors reported by firmware, then we
> want to continue with the current implementation that will inject the
> virtual abort. (kvm_inject_vabt)

So this needs to be in a comment there. This is generic code in the
sense that it is in drivers/acpi/ and it should say why it is doing that
special thing. I know, SEA is ARM-only, as far as I'm gathering from
reviewing this, but this behavior needs to be documented as it is not
obvious.

Thanks.

-- 
Regards/Gruss,
    Boris.

Good mailing practices for 400: avoid top-posting and trim the reply.

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