Subject: Re: [PATCH -V3 3/4] powerpc/kvm: Contiguous memory allocator based RMA allocation

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Tue, 02 Jul 2013 20:59:55 +0530

Alexander Graf <[email-masked]> writes:

> On 07/02/2013 07:45 AM, Aneesh Kumar K.V wrote:
>> From: "Aneesh Kumar K.V"<[email-masked]>
>>
>> Older version of power architecture use Real Mode Offset register and Real Mode Limit
>> Selector for mapping guest Real Mode Area. The guest RMA should be physically
>> contigous since we use the range when address translation is not enabled.
>>
>> This patch switch RMA allocation code to use contigous memory allocator. The patch
>> also remove the the linear allocator which not used any more
>>
>> Acked-by: Paul Mackerras<[email-masked]>
>> Signed-off-by: Aneesh Kumar K.V<[email-masked]>
>> ---

.... snip ....

>> diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
>> index 550f592..55c8519 100644
>> --- a/arch/powerpc/kvm/book3s_hv.c
>> +++ b/arch/powerpc/kvm/book3s_hv.c
>> @@ -1511,10 +1511,10 @@ static inline int lpcr_rmls(unsigned long rma_size)
>>
>>   static int kvm_rma_fault(struct vm_area_struct *vma, struct vm_fault *vmf)
>>   {
>> -	struct kvmppc_linear_info *ri = vma->vm_file->private_data;
>>   	struct page *page;
>> +	struct kvm_rma_info *ri = vma->vm_file->private_data;
>>
>> -	if (vmf->pgoff>= ri->npages)
>> +	if (vmf->pgoff>= kvm_rma_pages)
>>   		return VM_FAULT_SIGBUS;
>>
>>   	page = pfn_to_page(ri->base_pfn + vmf->pgoff);
>> @@ -1536,7 +1536,7 @@ static int kvm_rma_mmap(struct file *file, struct vm_area_struct *vma)
>>
>>   static int kvm_rma_release(struct inode *inode, struct file *filp)
>>   {
>> -	struct kvmppc_linear_info *ri = filp->private_data;
>> +	struct kvm_rma_info *ri = filp->private_data;
>>
>>   	kvm_release_rma(ri);
>>   	return 0;
>> @@ -1549,8 +1549,17 @@ static const struct file_operations kvm_rma_fops = {
>>
>>   long kvm_vm_ioctl_allocate_rma(struct kvm *kvm, struct kvm_allocate_rma *ret)
>>   {
>> -	struct kvmppc_linear_info *ri;
>>   	long fd;
>> +	struct kvm_rma_info *ri;
>> +	/*
>> +	 * Only do this on PPC970 in HV mode
>> +	 */
>> +	if (!cpu_has_feature(CPU_FTR_HVMODE) ||
>> +	    !cpu_has_feature(CPU_FTR_ARCH_201))
>> +		return -EINVAL;
>
> Is this really what we want? User space may want to use an RMA on POWER7 
> systems, no?

IIUC they will use virtual real mode area (VRMA) and not RMA

>
>> +
>> +	if (!kvm_rma_pages)
>> +		return -EINVAL;
>>
>>   	ri = kvm_alloc_rma();
>>   	if (!ri)
>> @@ -1560,7 +1569,7 @@ long kvm_vm_ioctl_allocate_rma(struct kvm *kvm, struct kvm_allocate_rma *ret)
>>   	if (fd<  0)
>>   		kvm_release_rma(ri);
>>
>> -	ret->rma_size = ri->npages<<  PAGE_SHIFT;
>> +	ret->rma_size = kvm_rma_pages<<  PAGE_SHIFT;
>>   	return fd;
>>   }
>>
>> @@ -1725,7 +1734,7 @@ static int kvmppc_hv_setup_htab_rma(struct kvm_vcpu *vcpu)
>>   {
>>   	int err = 0;
>>   	struct kvm *kvm = vcpu->kvm;
>> -	struct kvmppc_linear_info *ri = NULL;
>> +	struct kvm_rma_info *ri = NULL;
>>   	unsigned long hva;
>>   	struct kvm_memory_slot *memslot;
>>   	struct vm_area_struct *vma;
>> @@ -1803,7 +1812,7 @@ static int kvmppc_hv_setup_htab_rma(struct kvm_vcpu *vcpu)
>>
>>   	} else {
>>   		/* Set up to use an RMO region */
>> -		rma_size = ri->npages;
>> +		rma_size = kvm_rma_pages;
>>   		if (rma_size>  memslot->npages)
>>   			rma_size = memslot->npages;
>>   		rma_size<<= PAGE_SHIFT;
>> @@ -1831,14 +1840,14 @@ static int kvmppc_hv_setup_htab_rma(struct kvm_vcpu *vcpu)
>>   			/* POWER7 */
>>   			lpcr&= ~(LPCR_VPM0 | LPCR_VRMA_L);
>>   			lpcr |= rmls<<  LPCR_RMLS_SH;
>> -			kvm->arch.rmor = kvm->arch.rma->base_pfn<<  PAGE_SHIFT;
>> +			kvm->arch.rmor = ri->base_pfn<<  PAGE_SHIFT;
>>   		}
>>   		kvm->arch.lpcr = lpcr;
>>   		pr_info("KVM: Using RMO at %lx size %lx (LPCR = %lx)\n",
>>   			ri->base_pfn<<  PAGE_SHIFT, rma_size, lpcr);
>>
>>   		/* Initialize phys addrs of pages in RMO */
>> -		npages = ri->npages;
>> +		npages = kvm_rma_pages;
>>   		porder = __ilog2(npages);
>>   		physp = memslot->arch.slot_phys;
>>   		if (physp) {
>> diff --git a/arch/powerpc/kvm/book3s_hv_builtin.c b/arch/powerpc/kvm/book3s_hv_builtin.c
>> index 4b865c5..8cd0dae 100644
>> --- a/arch/powerpc/kvm/book3s_hv_builtin.c
>> +++ b/arch/powerpc/kvm/book3s_hv_builtin.c
>> @@ -21,13 +21,6 @@
>>   #include<asm/kvm_book3s.h>
>>
>>   #include "book3s_hv_cma.h"
>> -
>> -#define KVM_LINEAR_RMA		0
>> -#define KVM_LINEAR_HPT		1
>> -
>> -static void __init kvm_linear_init_one(ulong size, int count, int type);
>> -static struct kvmppc_linear_info *kvm_alloc_linear(int type);
>> -static void kvm_release_linear(struct kvmppc_linear_info *ri);
>>   /*
>>    * Hash page table alignment on newer cpus(CPU_FTR_ARCH_206)
>>    * should be power of 2.
>> @@ -37,19 +30,17 @@ static void kvm_release_linear(struct kvmppc_linear_info *ri);
>>    * By default we reserve 5% of memory for hash pagetable allocation.
>>    */
>>   static unsigned long kvm_cma_resv_ratio = 5;
>> -
>> -/*************** RMA *************/
>> -
>>   /*
>> - * This maintains a list of RMAs (real mode areas) for KVM guests to use.
>> + * We allocate RMAs (real mode areas) for KVM guests from the KVM CMA area.
>>    * Each RMA has to be physically contiguous and of a size that the
>>    * hardware supports.  PPC970 and POWER7 support 64MB, 128MB and 256MB,
>>    * and other larger sizes.  Since we are unlikely to be allocate that
>>    * much physically contiguous memory after the system is up and running,
>> - * we preallocate a set of RMAs in early boot for KVM to use.
>> + * we preallocate a set of RMAs in early boot using CMA.
>> + * should be power of 2.
>>    */
>> -static unsigned long kvm_rma_size = 64<<  20;	/* 64MB */
>> -static unsigned long kvm_rma_count;
>> +unsigned long kvm_rma_pages = (1<<  27)>>  PAGE_SHIFT;	/* 128MB */
>> +EXPORT_SYMBOL_GPL(kvm_rma_pages);
>>
>>   /* Work out RMLS (real mode limit selector) field value for a given RMA size.
>>      Assumes POWER7 or PPC970. */
>> @@ -79,35 +70,50 @@ static inline int lpcr_rmls(unsigned long rma_size)
>>
>>   static int __init early_parse_rma_size(char *p)
>>   {
>> -	if (!p)
>> -		return 1;
>> +	unsigned long kvm_rma_size;
>>
>> +	pr_debug("%s(%s)\n", __func__, p);
>> +	if (!p)
>> +		return -EINVAL;
>>   	kvm_rma_size = memparse(p,&p);
>> -
>> +	/*
>> +	 * Check that the requested size is one supported in hardware
>> +	 */
>> +	if (lpcr_rmls(kvm_rma_size)<  0) {
>> +		pr_err("RMA size of 0x%lx not supported\n", kvm_rma_size);
>> +		return -EINVAL;
>> +	}
>> +	kvm_rma_pages = kvm_rma_size>>  PAGE_SHIFT;
>>   	return 0;
>>   }
>>   early_param("kvm_rma_size", early_parse_rma_size);
>>
>> -static int __init early_parse_rma_count(char *p)
>> +struct kvm_rma_info *kvm_alloc_rma()
>>   {
>> -	if (!p)
>> -		return 1;
>> -
>> -	kvm_rma_count = simple_strtoul(p, NULL, 0);
>> -
>> -	return 0;
>> -}
>> -early_param("kvm_rma_count", early_parse_rma_count);
>> -
>> -struct kvmppc_linear_info *kvm_alloc_rma(void)
>> -{
>> -	return kvm_alloc_linear(KVM_LINEAR_RMA);
>> +	struct page *page;
>> +	struct kvm_rma_info *ri;
>> +
>> +	ri = kmalloc(sizeof(struct kvm_rma_info), GFP_KERNEL);
>> +	if (!ri)
>> +		return NULL;
>> +	page = kvm_alloc_cma(kvm_rma_pages, kvm_rma_pages);
>> +	if (!page)
>> +		goto err_out;
>> +	atomic_set(&ri->use_count, 1);
>> +	ri->base_pfn = page_to_pfn(page);
>> +	return ri;
>> +err_out:
>> +	kfree(ri);
>> +	return NULL;
>>   }
>>   EXPORT_SYMBOL_GPL(kvm_alloc_rma);
>>
>> -void kvm_release_rma(struct kvmppc_linear_info *ri)
>> +void kvm_release_rma(struct kvm_rma_info *ri)
>>   {
>> -	kvm_release_linear(ri);
>> +	if (atomic_dec_and_test(&ri->use_count)) {
>> +		kvm_release_cma(pfn_to_page(ri->base_pfn), kvm_rma_pages);
>> +		kfree(ri);
>> +	}
>>   }
>>   EXPORT_SYMBOL_GPL(kvm_release_rma);
>>
>> @@ -137,101 +143,6 @@ void kvm_release_hpt(struct page *page, unsigned long nr_pages)
>>   }
>>   EXPORT_SYMBOL_GPL(kvm_release_hpt);
>>
>> -/*************** generic *************/
>> -
>> -static LIST_HEAD(free_linears);
>> -static DEFINE_SPINLOCK(linear_lock);
>> -
>> -static void __init kvm_linear_init_one(ulong size, int count, int type)
>
> Please split the linar removal bits out into a separate patch :).
>
>

That was the way I had in the earlier patchset. That will cause a bisect
build break, because we consider warnings as error and we hit warning
of unused function.

I also realized that linear alloc functions are nearby and mostly fall
in the same hunk. Hence folded it back.

-aneesh