linux-kernel - Re: [RFC V2 PATCH 3/8] selftests: kvm: priv_memfd

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Date:   Thu, 12 May 2022 11:40:57 -0600
From:   Shuah Khan <skhan@...uxfoundation.org>
To:     Vishal Annapurve <vannapurve@...gle.com>, x86@...nel.org,
        kvm@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org
Cc:     pbonzini@...hat.com, vkuznets@...hat.com, wanpengli@...cent.com,
        jmattson@...gle.com, joro@...tes.org, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
        hpa@...or.com, shauh@...nel.org, yang.zhong@...el.com,
        drjones@...hat.com, ricarkol@...gle.com, aaronlewis@...gle.com,
        wei.w.wang@...el.com, kirill.shutemov@...ux.intel.com,
        corbet@....net, hughd@...gle.com, jlayton@...nel.org,
        bfields@...ldses.org, akpm@...ux-foundation.org,
        chao.p.peng@...ux.intel.com, yu.c.zhang@...ux.intel.com,
        jun.nakajima@...el.com, dave.hansen@...el.com,
        michael.roth@....com, qperret@...gle.com, steven.price@....com,
        ak@...ux.intel.com, david@...hat.com, luto@...nel.org,
        vbabka@...e.cz, marcorr@...gle.com, erdemaktas@...gle.com,
        pgonda@...gle.com, nikunj@....com, seanjc@...gle.com,
        diviness@...gle.com, Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [RFC V2 PATCH 3/8] selftests: kvm: priv_memfd_test: Add support
 for memory conversion

On 5/10/22 6:08 PM, Vishal Annapurve wrote:
> Add handling of explicit private/shared memory conversion using
> KVM_HC_MAP_GPA_RANGE and implicit memory conversion by handling
> KVM_EXIT_MEMORY_ERROR.
> 
> Signed-off-by: Vishal Annapurve <vannapurve@...gle.com>
> ---
>   tools/testing/selftests/kvm/priv_memfd_test.c | 87 +++++++++++++++++++
>   1 file changed, 87 insertions(+)
> 
> diff --git a/tools/testing/selftests/kvm/priv_memfd_test.c b/tools/testing/selftests/kvm/priv_memfd_test.c
> index bbb58c62e186..55e24c893b07 100644
> --- a/tools/testing/selftests/kvm/priv_memfd_test.c
> +++ b/tools/testing/selftests/kvm/priv_memfd_test.c
> @@ -155,6 +155,83 @@ static struct test_run_helper priv_memfd_testsuite[] = {
>   	},
>   };
>   
> +static void handle_vm_exit_hypercall(struct kvm_run *run,
> +	uint32_t test_id)
> +{
> +	uint64_t gpa, npages, attrs;
> +	int priv_memfd =
> +		priv_memfd_testsuite[test_id].priv_memfd;

Do you need this on a separate line? Doesn't looks like it will exceed
the limit with the tab?

> +	int ret;
> +	int fallocate_mode;
> +
> +	if (run->hypercall.nr != KVM_HC_MAP_GPA_RANGE) {
> +		TEST_FAIL("Unhandled Hypercall %lld\n",
> +					run->hypercall.nr);

Is this considered test fail or skip because of unmet dependency?
Also do you need run->hypercall.nr os a separate line?

> +	}
> +
> +	gpa = run->hypercall.args[0];
> +	npages = run->hypercall.args[1];
> +	attrs = run->hypercall.args[2];
> +
> +	if ((gpa < TEST_MEM_GPA) || ((gpa +
> +		(npages << MIN_PAGE_SHIFT)) > TEST_MEM_END)) {
> +		TEST_FAIL("Unhandled gpa 0x%lx npages %ld\n",
> +			gpa, npages);

Same question here about gpa, npages on a separate line? Also
align it with the previous line for readability.

TEST_FAIL("Unhandled gpa 0x%lx npages %ld\n",
	  gpa, npages);
  
> +	}
> +
> +	if (attrs & KVM_MAP_GPA_RANGE_ENCRYPTED)
> +		fallocate_mode = 0;
> +	else {
> +		fallocate_mode = (FALLOC_FL_PUNCH_HOLE |
> +			FALLOC_FL_KEEP_SIZE);
> +	}
> +	pr_info("Converting off 0x%lx pages 0x%lx to %s\n",
> +		(gpa - TEST_MEM_GPA), npages,
> +		fallocate_mode ?
> +			"shared" : "private");
> +	ret = fallocate(priv_memfd, fallocate_mode,
> +		(gpa - TEST_MEM_GPA),
> +		npages << MIN_PAGE_SHIFT);
> +	TEST_ASSERT(ret != -1,
> +		"fallocate failed in hc handling");
> +	run->hypercall.ret = 0;
> +}
> +
> +static void handle_vm_exit_memory_error(struct kvm_run *run,
> +	uint32_t test_id)
> +{
> +	uint64_t gpa, size, flags;
> +	int ret;
> +	int priv_memfd =
> +		priv_memfd_testsuite[test_id].priv_memfd;
> +	int fallocate_mode;
> +
> +	gpa = run->memory.gpa;
> +	size = run->memory.size;
> +	flags = run->memory.flags;
> +
> +	if ((gpa < TEST_MEM_GPA) || ((gpa + size)
> +					> TEST_MEM_END)) {
> +		TEST_FAIL("Unhandled gpa 0x%lx size 0x%lx\n",
> +			gpa, size);
> +	}
> +
> +	if (flags & KVM_MEMORY_EXIT_FLAG_PRIVATE)
> +		fallocate_mode = 0;
> +	else {
> +		fallocate_mode = (FALLOC_FL_PUNCH_HOLE |
> +				FALLOC_FL_KEEP_SIZE);
> +	}
> +	pr_info("Converting off 0x%lx size 0x%lx to %s\n",
> +		(gpa - TEST_MEM_GPA), size,
> +		fallocate_mode ?
> +			"shared" : "private");
> +	ret = fallocate(priv_memfd, fallocate_mode,
> +		(gpa - TEST_MEM_GPA), size);
> +	TEST_ASSERT(ret != -1,
> +		"fallocate failed in memory error handling");
> +}
> +
>   static void vcpu_work(struct kvm_vm *vm, uint32_t test_id)
>   {
>   	struct kvm_run *run;
> @@ -181,6 +258,16 @@ static void vcpu_work(struct kvm_vm *vm, uint32_t test_id)
>   			continue;
>   		}
>   
> +		if (run->exit_reason == KVM_EXIT_HYPERCALL) {
> +			handle_vm_exit_hypercall(run, test_id);
> +			continue;
> +		}
> +
> +		if (run->exit_reason == KVM_EXIT_MEMORY_ERROR) {
> +			handle_vm_exit_memory_error(run, test_id);
> +			continue;
> +		}
> +
>   		TEST_FAIL("Unhandled VCPU exit reason %d\n", run->exit_reason);
>   		break;
>   	}
> 

Looks like you can easily combine lines without running into # chars limit
for several lines of code in this patch. If you haven't already, run
checkpatch to make sure coding guidelines are honored.

thanks,
-- Shuah