On 03/02/2016 05:40 PM, Michael Ellerman wrote:
> On Wed, 2016-02-03 at 08:46:12 UTC, Anshuman Khandual wrote:
>> For partition running on PHYP, there can be a adjunct partition
>> which shares the virtual address range with the operating system.
>> Virtual address ranges which can be used by the adjunct partition
>> are communicated with virtual device node of the device tree with
>> a property known as "ibm,reserved-virtual-addresses". This patch
>> introduces a new function named 'validate_reserved_va_range' which
>> is called inside 'setup_system' to validate that these reserved
>> virtual address ranges do not overlap with the address ranges used
>> by the kernel for all supported memory contexts. This helps prevent
>> the possibility of getting return codes similar to H_RESOURCE for
>> H_PROTECT hcalls for conflicting HPTE entries.
>
> Good plan.
Thanks !
>
>> diff --git a/arch/powerpc/include/asm/mmu.h b/arch/powerpc/include/asm/mmu.h
>> index 3d5abfe..95257c1 100644
>> diff --git a/arch/powerpc/kernel/setup_64.c b/arch/powerpc/kernel/setup_64.c
>> index 5c03a6a..04bc592 100644
>> --- a/arch/powerpc/kernel/setup_64.c
>> +++ b/arch/powerpc/kernel/setup_64.c
>> @@ -546,6 +546,8 @@ void __init setup_system(void)
>> smp_release_cpus();
>> #endif
>>
>> + validate_reserved_va_range();
>> +
>
> I don't see why this can't just be an initcall in hash_utils_64.c, rather than
> being called from here.
That works, will change it.
>
>> pr_info("Starting Linux %s %s\n", init_utsname()->machine,
>> init_utsname()->version);
>>
>> diff --git a/arch/powerpc/mm/hash_utils_64.c
>> b/arch/powerpc/mm/hash_utils_64.c
>> index ba59d59..03adafc 100644
>> --- a/arch/powerpc/mm/hash_utils_64.c
>> +++ b/arch/powerpc/mm/hash_utils_64.c
>> @@ -810,6 +810,57 @@ void __init early_init_mmu(void)
>> slb_initialize();
>> }
>>
>> +/*
>> + * PAPR says that each record contains 3 * 32 bit element, hence 12 bytes.
>> + * First two element contains the abbreviated virtual address (high order
>> + * 32 bits and low order 32 bits generates the abbreviated virtual address
>> + * of 64 bits which need to be concatenated with 12 bits of 0 at the end
>> + * to generate the actual 76 bit reserved virtual address) and size of the
>> + * reserved virtual address range is encoded in next 32 bit element as
>> number
>> + * of 4K pages.
>> + */
>> +#define BYTES_PER_RVA_RECORD 12
>
> Please define a properly endian-annotated struct which encodes the layout.
something like this ?
struct reserved_va_record {
__be32 high_addr; /* High 32 bits of the abbreviated VA */
__be32 low_addr; /* Low 32 bits of the abbreviated VA */
__be32 nr_4k; /* VA range in multiple of 4K pages */
};
>
> It can be local to the function if that works.
>
Okay.
>> +/*
>> + * Linux uses 65 bits (MAX_PHYSMEM_BITS + CONTEXT_BITS) from available 78
>> + * bit wide virtual address range. As reserved virtual address range comes
>> + * as an abbreviated form of 64 bits, we will use a partial address mask
>> + * (65 bit mask >> 12) to match it for simplicity.
>> + */
>> +#define PARTIAL_USED_VA_MASK 0x1FFFFFFFFFFFFFULL
>
> Please calculate this from the appropriate constants. We don't want to have to
> update it in future.
Sure, I guess something like this works.
#define RVA_SKIPPED_BITS 12 /* This changes with PAPR */
#define USED_VA_BITS MAX_PHYSMEM_BITS + CONTEXT_BITS
#define PARTIAL_USED_VA_MASK ((1ULL << (USED_VA_BITS - RVA_SKIPPED_BITS)) -
1)
>
>> +void __init validate_reserved_va_range(void)
>> +{
>> + struct device_node *np;
>> + struct property *prop;
>> + unsigned int size, count, i;
>> + const __be32 *value;
>> + __be64 vaddr;
>> +
>> + np = of_find_node_by_name(NULL, "vdevice");
>> + if (!np)
>> + return;
>> +
>> + prop = of_find_property(np, "ibm,reserved-virtual-addresses", NULL);
>> + if (!prop)
>> + return;
>
> You don't need to do a find, the get below will do it for you.
Sure.
>
>> + value = of_get_property(np, "ibm,reserved-virtual-addresses", &size);
>> + if (!value)
>> + return;
>> +
>> + count = size / BYTES_PER_RVA_RECORD;
>> + for (i = 0; i < count; i++) {
>> + vaddr = ((__be64) value[i * 3] << 32) | value[i * 3 + 1];
>> + if (vaddr & ~PARTIAL_USED_VA_MASK) {
>
> How can it work to test a __be64 against a non-byte-swapped mask ? But like I
> said above, please do this with a struct and proper endian conversions.
sure.
>
>> + pr_info("Reserved virtual address range starting "
>> + "at [%llx000] verified for overlap\n", vaddr);
>
> This should print nothing in the success case.
Not even as a pr_devel level message ?
>
>> + continue;
>> + }
>> + BUG_ON("Reserved virtual address range overlapping");
>
> But here you should provide more detail. The first thing a debugger will need
> to know is what address overlapped.
Sure, will provide the starting VA and the size of the range.
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