I already do blurring for the shadow map texture, below is the shader code for the blurring.

#ifndef SEPERABLE_BLUR_KERNEL_SIZE
#define SEPERABLE_BLUR_KERNEL_SIZE 3
#endif

static const int BLUR_KERNEL_BEGIN = SEPERABLE_BLUR_KERNEL_SIZE / -2; 
static const int BLUR_KERNEL_END = SEPERABLE_BLUR_KERNEL_SIZE / 2 + 1;
static const float FLOAT_BLUR_KERNEL_SIZE = (float)SEPERABLE_BLUR_KERNEL_SIZE;

cbuffer cbblurVS : register( b2)
{
    int2        g_iWidthHeight            : packoffset( c0 );
    int            g_iKernelStart          : packoffset( c0.z );
    int            g_iKernelEnd            : packoffset( c0.w );
};

//--------------------------------------------------------------------------------------
// defines
//--------------------------------------------------------------------------------------

Texture2DArray g_txShadow : register( t5 );
SamplerState g_samShadow : register( s5 );

//--------------------------------------------------------------------------------------
// Input/Output structures
//--------------------------------------------------------------------------------------

struct PSIn
{
    float4      Pos        : SV_Position;        //Position
    float2      Tex        : TEXCOORD;            //Texture coordinate
    float2      ITex    : TEXCOORD2;
};

struct VSIn
{
    uint Pos    : SV_VertexID ;
};

PSIn VSMain(VSIn inn)
{
    PSIn output;

    output.Pos.y  = -1.0f + (inn.Pos%2) * 2.0f ;
    output.Pos.x  = -1.0f + (inn.Pos/2) * 2.0f;
    output.Pos.z = .5;
    output.Pos.w = 1;
    output.Tex.x = inn.Pos/2;
    output.Tex.y = 1.0f - inn.Pos%2;
    output.ITex.x = (float)(g_iWidthHeight.x * output.Tex.x);
    output.ITex.y = (float)(g_iWidthHeight.y * output.Tex.y);
    return output;
}

//float PSDepth

//------------------------------------------------------------------------------
// Logarithmic filtering
//------------------------------------------------------------------------------

float log_conv ( float x0, float X, float y0, float Y )
{
    return (X + log(x0 + (y0 * exp(Y - X))));
}

//--------------------------------------------------------------------------------------
// Pixel shader that performs bump mapping on the final vertex
//--------------------------------------------------------------------------------------
float2 PSBlurX(PSIn input) : SV_Target
{    
  
  
    float2 dep=0;
    [unroll]for ( int x = BLUR_KERNEL_BEGIN; x < BLUR_KERNEL_END; ++x ) {
        dep += g_txShadow.Sample( g_samShadow,  float3( input.Tex.x, input.Tex.y, 0 ), int2( x,0 ) ).rg;
    }
    dep /= FLOAT_BLUR_KERNEL_SIZE;
    return dep;  
    
//    return g_txShadow.Sample(g_samShadow,  float3(input.Tex.x, input.Tex.y, 0) ).rg;
    
}

//--------------------------------------------------------------------------------------
// Pixel shader that performs bump mapping on the final vertex
//--------------------------------------------------------------------------------------
float2 PSBlurY(PSIn input) : SV_Target
{    

    
    
    float2 dep=0;
    [unroll]for ( int y = BLUR_KERNEL_BEGIN; y < BLUR_KERNEL_END; ++y ) {
        dep += g_txShadow.Sample( g_samShadow,  float3( input.Tex.x, input.Tex.y, 0 ), int2( 0,y ) ).rg;
    }
    dep /= FLOAT_BLUR_KERNEL_SIZE;
    return dep;  
    
    //return g_txShadow.Sample(g_samShadow,  float3(input.Tex.x, input.Tex.y, 0) ).rg;
}