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From: Steven Price <steven.price@arm.com>
To: Jonathan Cameron <jonathan.cameron@huawei.com>
Cc: "Mark Rutland" <mark.rutland@arm.com>,
	kvm@vger.kernel.org, "Radim Krčmář" <rkrcmar@redhat.com>,
	"Marc Zyngier" <maz@kernel.org>,
	"Suzuki K Pouloze" <suzuki.poulose@arm.com>,
	linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
	"Russell King" <linux@armlinux.org.uk>,
	"James Morse" <james.morse@arm.com>,
	"Julien Thierry" <julien.thierry.kdev@gmail.com>,
	"Catalin Marinas" <catalin.marinas@arm.com>,
	"Paolo Bonzini" <pbonzini@redhat.com>,
	"Will Deacon" <will@kernel.org>,
	kvmarm@lists.cs.columbia.edu,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v3 04/10] KVM: Implement kvm_put_guest()
Date: Thu, 22 Aug 2019 11:37:06 +0100	[thread overview]
Message-ID: <003f509f-964b-2af0-d5da-1155fb4ec9d6@arm.com> (raw)
In-Reply-To: <20190822112930.000052db@huawei.com>

On 22/08/2019 11:29, Jonathan Cameron wrote:
> On Wed, 21 Aug 2019 16:36:50 +0100
> Steven Price <steven.price@arm.com> wrote:
> 
>> kvm_put_guest() is analogous to put_user() - it writes a single value to
>> the guest physical address. The implementation is built upon put_user()
>> and so it has the same single copy atomic properties.
>>
>> Signed-off-by: Steven Price <steven.price@arm.com>
>> ---
>>  include/linux/kvm_host.h | 24 ++++++++++++++++++++++++
>>  1 file changed, 24 insertions(+)
>>
>> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
>> index fcb46b3374c6..e154a1897e20 100644
>> --- a/include/linux/kvm_host.h
>> +++ b/include/linux/kvm_host.h
>> @@ -746,6 +746,30 @@ int kvm_write_guest_offset_cached(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
>>  				  unsigned long len);
>>  int kvm_gfn_to_hva_cache_init(struct kvm *kvm, struct gfn_to_hva_cache *ghc,
>>  			      gpa_t gpa, unsigned long len);
>> +
>> +#define __kvm_put_guest(kvm, gfn, offset, value, type)			\
>> +({									\
>> +	unsigned long __addr = gfn_to_hva(kvm, gfn);			\
>> +	type __user *__uaddr = (type __user *)(__addr + offset);	\
>> +	int __ret = 0;							\
> 
> Why initialize __ret?

Good question. Actually looking at this again if I reorder this to be
pessimistic I can make it shorter:

	int __ret = -EFAULT;

	if (!kvm_is_error_hva(__addr))
		__ret = put_user(value, __uaddr);
	if (!__ret)
		mark_page_dirty(kvm, gfn);				
	__ret;

Thanks for taking a look.

Steve

>> +									\
>> +	if (kvm_is_error_hva(__addr))					\
>> +		__ret = -EFAULT;					\
>> +	else								\
>> +		__ret = put_user(value, __uaddr);			\
>> +	if (!__ret)							\
>> +		mark_page_dirty(kvm, gfn);				\
>> +	__ret;								\
>> +})
>> +
>> +#define kvm_put_guest(kvm, gpa, value, type)				\
>> +({									\
>> +	gpa_t __gpa = gpa;						\
>> +	struct kvm *__kvm = kvm;					\
>> +	__kvm_put_guest(__kvm, __gpa >> PAGE_SHIFT,			\
>> +			offset_in_page(__gpa), (value), type);		\
>> +})
>> +
>>  int kvm_clear_guest_page(struct kvm *kvm, gfn_t gfn, int offset, int len);
>>  int kvm_clear_guest(struct kvm *kvm, gpa_t gpa, unsigned long len);
>>  struct kvm_memory_slot *gfn_to_memslot(struct kvm *kvm, gfn_t gfn);
> 
> 
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
> 


  reply	other threads:[~2019-08-22 10:37 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-21 15:36 [PATCH v3 00/10] arm64: Stolen time support Steven Price
2019-08-21 15:36 ` [PATCH v3 01/10] KVM: arm64: Document PV-time interface Steven Price
2019-08-27  8:44   ` Christoffer Dall
2019-08-28 11:23     ` Steven Price
2019-08-27  8:57   ` Christoffer Dall
2019-08-28 12:09     ` Steven Price
2019-08-30  9:22       ` Christoffer Dall
2019-08-28 13:49     ` Christoffer Dall
2019-08-29 15:21       ` Steven Price
2019-08-29 17:15   ` Andrew Jones
2019-08-30  8:35     ` Steven Price
2019-08-21 15:36 ` [PATCH v3 02/10] KVM: arm/arm64: Factor out hypercall handling from PSCI code Steven Price
2019-08-21 15:36 ` [PATCH v3 03/10] KVM: arm64: Implement PV_FEATURES call Steven Price
2019-08-21 15:36 ` [PATCH v3 04/10] KVM: Implement kvm_put_guest() Steven Price
2019-08-22 10:29   ` Jonathan Cameron
2019-08-22 10:37     ` Steven Price [this message]
2019-08-22 15:28   ` Sean Christopherson
2019-08-22 15:46     ` Steven Price
2019-08-22 16:24       ` Sean Christopherson
2019-08-23 10:33         ` Steven Price
2019-08-21 15:36 ` [PATCH v3 05/10] KVM: arm64: Support stolen time reporting via shared structure Steven Price
2019-08-22 10:39   ` Jonathan Cameron
2019-08-22 11:00     ` Steven Price
2019-08-23 12:07   ` Zenghui Yu
2019-08-23 13:23     ` Steven Price
2019-08-21 15:36 ` [PATCH v3 06/10] KVM: Allow kvm_device_ops to be const Steven Price
2019-08-21 15:36 ` [PATCH v3 07/10] KVM: arm64: Provide a PV_TIME device to user space Steven Price
2019-08-22 10:57   ` Jonathan Cameron
2019-08-22 11:11     ` Steven Price
2019-08-22 11:48       ` Jonathan Cameron
2019-08-21 15:36 ` [PATCH v3 08/10] arm/arm64: Provide a wrapper for SMCCC 1.1 calls Steven Price
2019-08-21 15:36 ` [PATCH v3 09/10] arm/arm64: Make use of the SMCCC 1.1 wrapper Steven Price
2019-08-21 15:36 ` [PATCH v3 10/10] arm64: Retrieve stolen time as paravirtualized guest Steven Price
2019-08-23 11:45   ` Zenghui Yu
2019-08-23 14:22     ` Steven Price
2019-08-27 12:43       ` Zenghui Yu

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