Re: [PATCH v3 7/8] x86/sev: Add full support for a segmented RMP table

[Tom Lendacky <thomas.lendacky@amd.com>]

On 10/18/24 03:37, Neeraj Upadhyay wrote:
> 
> 
>>  
>> @@ -196,7 +203,42 @@ static void __init __snp_fixup_e820_tables(u64 pa)
>>  void __init snp_fixup_e820_tables(void)
>>  {
>>  	__snp_fixup_e820_tables(probed_rmp_base);
>> -	__snp_fixup_e820_tables(probed_rmp_base + probed_rmp_size);
>> +
>> +	if (RMP_IS_SEGMENTED(rmp_cfg)) {
>> +		unsigned long size;
>> +		unsigned int i;
>> +		u64 pa, *rst;
>> +
>> +		pa = probed_rmp_base;
>> +		pa += RMPTABLE_CPU_BOOKKEEPING_SZ;
>> +		pa += RMP_SEGMENT_TABLE_SIZE;
>> +		__snp_fixup_e820_tables(pa);
>> +
>> +		pa -= RMP_SEGMENT_TABLE_SIZE;
>> +		rst = early_memremap(pa, RMP_SEGMENT_TABLE_SIZE);
>> +		if (!rst)
>> +			return;
>> +
>> +		for (i = 0; i < rst_max_index; i++) {
>> +			pa = RST_ENTRY_SEGMENT_BASE(rst[i]);
>> +			size = RST_ENTRY_MAPPED_SIZE(rst[i]);
>> +			if (!size)
>> +				continue;
>> +
>> +			__snp_fixup_e820_tables(pa);
>> +
>> +			/* Mapped size in GB */
>> +			size *= (1UL << 30);
> 
> nit: size <<= 30 ?

Yeah, might be clearer.

> 
>> +			if (size > rmp_segment_coverage_size)
>> +				size = rmp_segment_coverage_size;
>> +
>> +			__snp_fixup_e820_tables(pa + size);
> 
> I might have understood this wrong, but is this call meant to fixup segmented
> rmp table end. So, is below is required?
> 
> size  = PHYS_PFN(size);
> size <<= 4;
> __snp_fixup_e820_tables(pa + size);

Good catch. Yes, it is supposed to be checking the end of the RMP segment
which should be the number of entries and not the mapped size.

> 
>> +		}
>> +
>> +		early_memunmap(rst, RMP_SEGMENT_TABLE_SIZE);
>> +	} else {
>> +		__snp_fixup_e820_tables(probed_rmp_base + probed_rmp_size);
>> +	}
>>  }
>>  
> 
> ...
> 
>> +static bool __init segmented_rmptable_setup(void)
>> +{
>> +	u64 rst_pa, *rst, pa, ram_pa_end, ram_pa_max;
>> +	unsigned int i, max_index;
>> +
>> +	if (!probed_rmp_base)
>> +		return false;
>> +
>> +	if (!alloc_rmp_segment_table())
>> +		return false;
>> +
>> +	/* Map the RMP Segment Table */
>> +	rst_pa = probed_rmp_base + RMPTABLE_CPU_BOOKKEEPING_SZ;
>> +	rst = memremap(rst_pa, RMP_SEGMENT_TABLE_SIZE, MEMREMAP_WB);
>> +	if (!rst) {
>> +		pr_err("Failed to map RMP segment table addr %#llx\n", rst_pa);
>> +		goto e_free;
>> +	}
>> +
>> +	/* Get the address for the end of system RAM */
>> +	ram_pa_max = max_pfn << PAGE_SHIFT;
>> +
>> +	/* Process each RMP segment */
>> +	max_index = 0;
>> +	ram_pa_end = 0;
>> +	for (i = 0; i < rst_max_index; i++) {
>> +		u64 rmp_segment, rmp_size, mapped_size;
>> +
>> +		mapped_size = RST_ENTRY_MAPPED_SIZE(rst[i]);
>> +		if (!mapped_size)
>> +			continue;
>> +
>> +		max_index = i;
>> +
>> +		/* Mapped size in GB */
>> +		mapped_size *= (1ULL << 30);
> 
> nit: mapped_size <<= 30 ?

Ditto.

> 
>> +		if (mapped_size > rmp_segment_coverage_size)
>> +			mapped_size = rmp_segment_coverage_size;
>> +
>> +		rmp_segment = RST_ENTRY_SEGMENT_BASE(rst[i]);
>> +
>> +		rmp_size = PHYS_PFN(mapped_size);
>> +		rmp_size <<= 4;
>> +
>> +		pa = (u64)i << rmp_segment_coverage_shift;
>> +
>> +		/* Some segments may be for MMIO mapped above system RAM */
>> +		if (pa < ram_pa_max)
>> +			ram_pa_end = pa + mapped_size;
>> +
>> +		if (!alloc_rmp_segment_desc(rmp_segment, rmp_size, pa))
>> +			goto e_unmap;
>> +
>> +		pr_info("RMP segment %u physical address [%#llx - %#llx] covering [%#llx - %#llx]\n",
>> +			i, rmp_segment, rmp_segment + rmp_size - 1, pa, pa + mapped_size - 1);
>> +	}
>> +
>> +	if (ram_pa_max > ram_pa_end) {
>> +		pr_err("Segmented RMP does not cover full system RAM (expected 0x%llx got 0x%llx)\n",
>> +		       ram_pa_max, ram_pa_end);
>> +		goto e_unmap;
>> +	}
>> +
>> +	/* Adjust the maximum index based on the found segments */
>> +	rst_max_index = max_index + 1;
>> +
>> +	memunmap(rst);
>> +
>> +	return true;
>> +
>> +e_unmap:
>> +	memunmap(rst);
>> +
>> +e_free:
>> +	free_rmp_segment_table();
>> +
>> +	return false;
>> +}
>> +
> 
> ...
> 
>>  
>> +static bool probe_segmented_rmptable_info(void)
>> +{
>> +	unsigned int eax, ebx, segment_shift, segment_shift_min, segment_shift_max;
>> +	u64 rmp_base, rmp_end;
>> +
>> +	rdmsrl(MSR_AMD64_RMP_BASE, rmp_base);
>> +	rdmsrl(MSR_AMD64_RMP_END, rmp_end);
>> +
>> +	if (!(rmp_base & RMP_ADDR_MASK)) {
>> +		pr_err("Memory for the RMP table has not been reserved by BIOS\n");
>> +		return false;
>> +	}
>> +
>> +	WARN_ONCE(rmp_end & RMP_ADDR_MASK,
>> +		  "Segmented RMP enabled but RMP_END MSR is non-zero\n");
>> +
>> +	/* Obtain the min and max supported RMP segment size */
>> +	eax = cpuid_eax(0x80000025);
>> +	segment_shift_min = eax & GENMASK(5, 0);
>> +	segment_shift_max = (eax & GENMASK(11, 6)) >> 6;
>> +
>> +	/* Verify the segment size is within the supported limits */
>> +	segment_shift = MSR_AMD64_RMP_SEGMENT_SHIFT(rmp_cfg);
>> +	if (segment_shift > segment_shift_max || segment_shift < segment_shift_min) {
>> +		pr_err("RMP segment size (%u) is not within advertised bounds (min=%u, max=%u)\n",
>> +		       segment_shift, segment_shift_min, segment_shift_max);
>> +		return false;
>> +	}
>> +
>> +	/* Override the max supported RST index if a hardware limit exists */
>> +	ebx = cpuid_ebx(0x80000025);
>> +	if (ebx & BIT(10))
>> +		rst_max_index = ebx & GENMASK(9, 0);
>> +
>> +	set_rmp_segment_info(segment_shift);
>> +
>> +	probed_rmp_base = rmp_base;
>> +	probed_rmp_size = 0;
>> +
>> +	pr_info("RMP segment table physical address [0x%016llx - 0x%016llx]\n",
>> +		rmp_base, rmp_base + RMPTABLE_CPU_BOOKKEEPING_SZ + RMP_SEGMENT_TABLE_SIZE);
>> +
> 
> rmp_base + RMPTABLE_CPU_BOOKKEEPING_SZ, rmp_base + RMPTABLE_CPU_BOOKKEEPING_SZ + RMP_SEGMENT_TABLE_SIZE);

I really want the full range printed, which includes the bookkeeping area.
So maybe the text could be clearer, let me think about that.

Thanks,
Tom

> 
> 
> - Neeraj
> 
>> +	return true;
>> +}
>> +