linux-kernel - Re: [PATCH] efi: capsule: allocate whole capsule into virtual memory

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Date:	Thu, 21 Jul 2016 15:05:52 -0600
From:	"Christ, Austin" <austinwc@...eaurora.org>
To:	Matt Fleming <matt@...eblueprint.co.uk>
Cc:	linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, jbrasen@...eaurora.org,
	Kweh Hock Leong <hock.leong.kweh@...el.com>,
	Bryan O'Donoghue <pure.logic@...us-software.ie>
Subject: Re: [PATCH] efi: capsule: allocate whole capsule into virtual memory

Hey Matt,


On 7/21/2016 7:12 AM, Matt Fleming wrote:
> On Fri, 15 Jul, at 10:41:31AM, Christ, Austin wrote:
>> According to UEFI 2.6 section 7.5.3, the capsule should be in contiguous
>> virtual memory and firmware may consume the capsule immediately. To
>> correctly implement this functionality, the kernel driver needs to vmap
>> the entire capsule at the time it is made available to firmware.
>>
>> The virtual allocation of the capsule update has been changed from kmap,
>> which was only allocating the first page of the update, to vmap and
>> allocates the entire data payload.
>>
>> Signed-off-by: Austin Christ <austinwc@...eaurora.org>
>> ---
>>   drivers/firmware/efi/capsule-loader.c | 6 ++++--
>>   1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/firmware/efi/capsule-loader.c b/drivers/firmware/efi/capsule-loader.c
>> index c99c24b..c4f3c20 100644
>> --- a/drivers/firmware/efi/capsule-loader.c
>> +++ b/drivers/firmware/efi/capsule-loader.c
>> @@ -16,6 +16,7 @@
>>   #include <linux/slab.h>
>>   #include <linux/mutex.h>
>>   #include <linux/efi.h>
>> +#include <linux/vmalloc.h>
>>   
>>   #define NO_FURTHER_WRITE_ACTION -1
>>   
>> @@ -108,14 +109,15 @@ static ssize_t efi_capsule_submit_update(struct capsule_info *cap_info)
>>   	int ret;
>>   	void *cap_hdr_temp;
>>   
>> -	cap_hdr_temp = kmap(cap_info->pages[0]);
>> +	cap_hdr_temp = vmap(cap_info->pages, cap_info->index,
>> +			VM_MAP, PAGE_KERNEL);
>>   	if (!cap_hdr_temp) {
>>   		pr_debug("%s: kmap() failed\n", __func__);
>>   		return -EFAULT;
>>   	}
>>   
>>   	ret = efi_capsule_update(cap_hdr_temp, cap_info->pages);
>> -	kunmap(cap_info->pages[0]);
>> +	vunmap(cap_hdr_temp);
>>   	if (ret) {
>>   		pr_err("%s: efi_capsule_update() failed\n", __func__);
>>   		return ret;
> Looks OK to me but could you also update the comments above
> efi_capsule_update() that mention the virtual mapping only being
> required for the first page?
That's a great point. The comments will be updated in v2.

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Thanks,
Austin